diff --git a/vlib/net/websocket/utils.v b/vlib/net/websocket/utils.v
index 50feeffb30..cf16d16aea 100644
--- a/vlib/net/websocket/utils.v
+++ b/vlib/net/websocket/utils.v
@@ -23,7 +23,7 @@ fn htonl64(payload_len u64) []u8 {
 
 // create_masking_key returns a new masking key to use when masking websocket messages
 fn create_masking_key() []u8 {
-	return rand.bytes(4) or { [0, 0, 0, 0] }
+	return rand.bytes(4) or { [u8(0), 0, 0, 0] }
 }
 
 // create_key_challenge_response creates a key challenge response from security key
diff --git a/vlib/picohttpparser/misc_test.v b/vlib/picohttpparser/misc_test.v
index a3fb7a54b8..0cdff9f033 100644
--- a/vlib/picohttpparser/misc_test.v
+++ b/vlib/picohttpparser/misc_test.v
@@ -19,7 +19,10 @@ pub fn test_u64toa_large_values() {
 		mut buf := [20]u8{}
 
 		len := unsafe {
-			u64toa(&buf[0], v) or { assert err.msg() == 'Maximum size of 100MB exceeded!' }
+			u64toa(&buf[0], v) or {
+				assert err.msg() == 'Maximum size of 100MB exceeded!'
+				0
+			}
 		}
 
 		if v < 100_000_000 {
@@ -38,7 +41,10 @@ pub fn test_u64toa_edge_cases() {
 
 	// Test zero value
 	len := unsafe {
-		u64toa(&buf[0], 0) or { assert false }
+		u64toa(&buf[0], 0) or {
+			assert false
+			0
+		}
 	}
 
 	assert len == 1
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index c9a22a27da..c3e11bab6e 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -126,6 +126,7 @@ mut:
 	generic_fns                      map[string]bool // register generic fns that needs recheck once
 	inside_sql                       bool            // to handle sql table fields pseudo variables
 	inside_selector_expr             bool
+	inside_or_block_value            bool // true inside or-block where its value is used `f(g() or { true })`
 	inside_interface_deref           bool
 	inside_decl_rhs                  bool
 	inside_if_guard                  bool // true inside the guard condition of `if x := opt() {}`
@@ -1354,16 +1355,25 @@ fn (mut c Checker) check_or_expr(node ast.OrExpr, ret_type ast.Type, expr_return
 		return
 	}
 	if node.stmts.len == 0 {
-		if ret_type != ast.void_type {
-			// x := f() or {}
-			c.error('assignment requires a non empty `or {}` block', node.pos)
+		if expr is ast.CallExpr && expr.is_return_used {
+			// x := f() or {}, || f() or {} etc
+			c.error('expression requires a non empty `or {}` block', node.pos)
+		} else if expr !is ast.CallExpr && ret_type != ast.void_type {
+			// _ := sql db {... } or { }
+			c.error('expression requires a non empty `or {}` block', node.pos)
 		}
 		// allow `f() or {}`
 		return
 	}
 	mut valid_stmts := node.stmts.filter(it !is ast.SemicolonStmt)
 	mut last_stmt := if valid_stmts.len > 0 { valid_stmts.last() } else { node.stmts.last() }
-	c.check_or_last_stmt(mut last_stmt, ret_type, expr_return_type.clear_option_and_result())
+	if expr !is ast.CallExpr || (expr is ast.CallExpr && expr.is_return_used) {
+		// requires a block returning an unwrapped type of expr return type
+		c.check_or_last_stmt(mut last_stmt, ret_type, expr_return_type.clear_option_and_result())
+	} else {
+		// allow f() or { var = 123 }
+		c.check_or_last_stmt(mut last_stmt, ast.void_type, expr_return_type.clear_option_and_result())
+	}
 }
 
 fn (mut c Checker) check_or_last_stmt(mut stmt ast.Stmt, ret_type ast.Type, expr_return_type ast.Type) {
@@ -1372,6 +1382,10 @@ fn (mut c Checker) check_or_last_stmt(mut stmt ast.Stmt, ret_type ast.Type, expr
 			ast.ExprStmt {
 				c.expected_type = ret_type
 				c.expected_or_type = ret_type.clear_option_and_result()
+				if c.inside_or_block_value && stmt.expr is ast.None && ret_type.has_flag(.option) {
+					// return call() or { none } where fn returns an Option type
+					return
+				}
 				last_stmt_typ := c.expr(mut stmt.expr)
 				if last_stmt_typ.has_flag(.option) || last_stmt_typ == ast.none_type {
 					if stmt.expr in [ast.Ident, ast.SelectorExpr, ast.CallExpr, ast.None, ast.CastExpr] {
@@ -1437,9 +1451,11 @@ fn (mut c Checker) check_or_last_stmt(mut stmt ast.Stmt, ret_type ast.Type, expr
 			}
 			ast.Return {}
 			else {
-				expected_type_name := c.table.type_to_str(ret_type.clear_option_and_result())
-				c.error('last statement in the `or {}` block should be an expression of type `${expected_type_name}` or exit parent scope',
-					stmt.pos)
+				if stmt !is ast.AssertStmt || c.inside_or_block_value {
+					expected_type_name := c.table.type_to_str(ret_type.clear_option_and_result())
+					c.error('last statement in the `or {}` block should be an expression of type `${expected_type_name}` or exit parent scope',
+						stmt.pos)
+				}
 			}
 		}
 	} else if mut stmt is ast.ExprStmt {
diff --git a/vlib/v/checker/fn.v b/vlib/v/checker/fn.v
index 76fba44f17..59b4394004 100644
--- a/vlib/v/checker/fn.v
+++ b/vlib/v/checker/fn.v
@@ -737,9 +737,17 @@ fn (mut c Checker) call_expr(mut node ast.CallExpr) ast.Type {
 			}
 		}
 	}
+	old_expected_or_type := c.expected_or_type
 	c.expected_or_type = node.return_type.clear_flag(.result)
 	c.stmts_ending_with_expression(mut node.or_block.stmts, c.expected_or_type)
-	c.expected_or_type = ast.void_type
+
+	if node.or_block.kind == .block {
+		old_inside_or_block_value := c.inside_or_block_value
+		c.inside_or_block_value = true
+		c.check_or_expr(node.or_block, typ, c.expected_or_type, node)
+		c.inside_or_block_value = old_inside_or_block_value
+	}
+	c.expected_or_type = old_expected_or_type
 
 	if !c.inside_const && c.table.cur_fn != unsafe { nil } && !c.table.cur_fn.is_main
 		&& !c.table.cur_fn.is_test {
diff --git a/vlib/v/checker/lambda_expr.v b/vlib/v/checker/lambda_expr.v
index d7c628030d..464e546ab6 100644
--- a/vlib/v/checker/lambda_expr.v
+++ b/vlib/v/checker/lambda_expr.v
@@ -65,6 +65,9 @@ pub fn (mut c Checker) lambda_expr(mut node ast.LambdaExpr, exp_typ ast.Type) as
 				is_expr: false
 				typ:     return_type
 			}
+			if mut node.expr is ast.CallExpr && node.expr.is_return_used {
+				node.expr.is_return_used = false
+			}
 		} else {
 			stmts << ast.Return{
 				pos:   node.pos
diff --git a/vlib/v/checker/or_block_assert_err.out b/vlib/v/checker/or_block_assert_err.out
new file mode 100644
index 0000000000..1074f6e07e
--- /dev/null
+++ b/vlib/v/checker/or_block_assert_err.out
@@ -0,0 +1,12 @@
+vlib/v/checker/or_block_assert_err.vv:10:22: error: last statement in the `or {}` block should be an expression of type `int` or exit parent scope
+    8 | 
+    9 | f() or { assert true }
+   10 | a := f() or { assert true }
+      |                      ~~~~~~
+   11 | dump(a)
+   12 | g(f() or { assert true })
+vlib/v/checker/or_block_assert_err.vv:12:19: error: last statement in the `or {}` block should be an expression of type `int` or exit parent scope
+   10 | a := f() or { assert true }
+   11 | dump(a)
+   12 | g(f() or { assert true })
+      |                   ~~~~~~
diff --git a/vlib/v/checker/or_block_assert_err.vv b/vlib/v/checker/or_block_assert_err.vv
new file mode 100644
index 0000000000..29b5dad552
--- /dev/null
+++ b/vlib/v/checker/or_block_assert_err.vv
@@ -0,0 +1,12 @@
+fn g(x int) {
+	dump(x)
+}
+
+fn f() ?int {
+	return none
+}
+
+f() or { assert true }
+a := f() or { assert true }
+dump(a)
+g(f() or { assert true })
diff --git a/vlib/v/checker/tests/call_empty_or_block_err.out b/vlib/v/checker/tests/call_empty_or_block_err.out
new file mode 100644
index 0000000000..eed78724a9
--- /dev/null
+++ b/vlib/v/checker/tests/call_empty_or_block_err.out
@@ -0,0 +1,56 @@
+vlib/v/checker/tests/call_empty_or_block_err.vv:9:2: warning: unused variable: `a`
+    7 | 
+    8 | fn main() {
+    9 |     a := foo() or { foo() or {} }
+      |     ^
+   10 | 
+   11 |     // must be error
+vlib/v/checker/tests/call_empty_or_block_err.vv:12:2: warning: unused variable: `y`
+   10 | 
+   11 |     // must be error
+   12 |     y := if c := foo() {
+      |     ^
+   13 |         dump(c)
+   14 |         bar() or {}
+vlib/v/checker/tests/call_empty_or_block_err.vv:20:2: warning: unused variable: `z`
+   18 | 
+   19 |     // ok
+   20 |     z := if d := foo() {
+      |     ^
+   21 |         dump(d)
+   22 |         bar() or {}
+vlib/v/checker/tests/call_empty_or_block_err.vv:29:2: warning: unused variable: `w`
+   27 | 
+   28 |     // ok
+   29 |     w := foo() or {
+      |     ^
+   30 |         bar() or {}
+   31 |         false
+vlib/v/checker/tests/call_empty_or_block_err.vv:35:2: warning: unused variable: `b`
+   33 | 
+   34 |     // ok
+   35 |     b := foo() or {
+      |     ^
+   36 |         foo() or {}
+   37 |         false
+vlib/v/checker/tests/call_empty_or_block_err.vv:9:24: error: expression requires a non empty `or {}` block
+    7 | 
+    8 | fn main() {
+    9 |     a := foo() or { foo() or {} }
+      |                           ~~~~~
+   10 | 
+   11 |     // must be error
+vlib/v/checker/tests/call_empty_or_block_err.vv:14:9: error: expression requires a non empty `or {}` block
+   12 |     y := if c := foo() {
+   13 |         dump(c)
+   14 |         bar() or {}
+      |               ~~~~~
+   15 |     } else {
+   16 |         false
+vlib/v/checker/tests/call_empty_or_block_err.vv:14:3: error: the final expression in `if` or `match`, must have a value of a non-void type
+   12 |     y := if c := foo() {
+   13 |         dump(c)
+   14 |         bar() or {}
+      |         ~~~~~
+   15 |     } else {
+   16 |         false
diff --git a/vlib/v/checker/tests/call_empty_or_block_err.vv b/vlib/v/checker/tests/call_empty_or_block_err.vv
new file mode 100644
index 0000000000..f58e00bad1
--- /dev/null
+++ b/vlib/v/checker/tests/call_empty_or_block_err.vv
@@ -0,0 +1,39 @@
+fn foo() !bool {
+	return true
+}
+
+fn bar() ! {
+}
+
+fn main() {
+	a := foo() or { foo() or {} }
+
+	// must be error
+	y := if c := foo() {
+		dump(c)
+		bar() or {}
+	} else {
+		false
+	}
+
+	// ok
+	z := if d := foo() {
+		dump(d)
+		bar() or {}
+		true
+	} else {
+		false
+	}
+
+	// ok
+	w := foo() or {
+		bar() or {}
+		false
+	}
+
+	// ok
+	b := foo() or {
+		foo() or {}
+		false
+	}
+}
diff --git a/vlib/v/checker/tests/fn_call_or_block_err.out b/vlib/v/checker/tests/fn_call_or_block_err.out
new file mode 100644
index 0000000000..bb43071669
--- /dev/null
+++ b/vlib/v/checker/tests/fn_call_or_block_err.out
@@ -0,0 +1,6 @@
+vlib/v/checker/tests/fn_call_or_block_err.vv:7:18: error: wrong return type `int literal` in the `or {}` block, expected `string`
+    5 | }
+    6 | 
+    7 | y := Aa(f() or { 2 })
+      |                  ^
+    8 | println(y)
diff --git a/vlib/v/checker/tests/fn_call_or_block_err.vv b/vlib/v/checker/tests/fn_call_or_block_err.vv
new file mode 100644
index 0000000000..db43465a87
--- /dev/null
+++ b/vlib/v/checker/tests/fn_call_or_block_err.vv
@@ -0,0 +1,8 @@
+type Aa = string | int
+
+fn f() !string {
+	return ''
+}
+
+y := Aa(f() or { 2 })
+println(y)
diff --git a/vlib/v/checker/tests/lambda_or_block_err.out b/vlib/v/checker/tests/lambda_or_block_err.out
new file mode 100644
index 0000000000..62964daf63
--- /dev/null
+++ b/vlib/v/checker/tests/lambda_or_block_err.out
@@ -0,0 +1,14 @@
+vlib/v/checker/tests/lambda_or_block_err.vv:10:10: error: cannot use `!int` as type `int` in return argument
+    8 | 
+    9 | fn main() {
+   10 |     foo(|i| bar(i))
+      |             ~~~~~~
+   11 |     foo(|i| bar(i) or {})
+   12 |     foo(|i| bar(i) or { 0 })
+vlib/v/checker/tests/lambda_or_block_err.vv:11:17: error: expression requires a non empty `or {}` block
+    9 | fn main() {
+   10 |     foo(|i| bar(i))
+   11 |     foo(|i| bar(i) or {})
+      |                    ~~~~~
+   12 |     foo(|i| bar(i) or { 0 })
+   13 | }
diff --git a/vlib/v/checker/tests/lambda_or_block_err.vv b/vlib/v/checker/tests/lambda_or_block_err.vv
new file mode 100644
index 0000000000..18314d07b4
--- /dev/null
+++ b/vlib/v/checker/tests/lambda_or_block_err.vv
@@ -0,0 +1,13 @@
+fn foo(callback fn (int) int) {
+	dump([1, 2, 3].map(callback))
+}
+
+fn bar(a int) !int {
+	return a
+}
+
+fn main() {
+	foo(|i| bar(i))
+	foo(|i| bar(i) or {})
+	foo(|i| bar(i) or { 0 })
+}
diff --git a/vlib/v/checker/tests/or_block_check_err.out b/vlib/v/checker/tests/or_block_check_err.out
index c4fb27bba8..854bbe1d66 100644
--- a/vlib/v/checker/tests/or_block_check_err.out
+++ b/vlib/v/checker/tests/or_block_check_err.out
@@ -1,11 +1,11 @@
-vlib/v/checker/tests/or_block_check_err.vv:6:36: error: assignment requires a non empty `or {}` block
+vlib/v/checker/tests/or_block_check_err.vv:6:36: error: expression requires a non empty `or {}` block
     4 | 
     5 | fn main() {
     6 |     _ = callexpr_with_or_block_call() or {}.replace('a', 'b')
       |                                       ~~~~~
     7 |     _ = (callexpr_with_or_block_call() or {}).replace('a', 'b')
     8 |
-vlib/v/checker/tests/or_block_check_err.vv:7:37: error: assignment requires a non empty `or {}` block
+vlib/v/checker/tests/or_block_check_err.vv:7:37: error: expression requires a non empty `or {}` block
     5 | fn main() {
     6 |     _ = callexpr_with_or_block_call() or {}.replace('a', 'b')
     7 |     _ = (callexpr_with_or_block_call() or {}).replace('a', 'b')
diff --git a/vlib/v/checker/tests/orm_no_default_value.out b/vlib/v/checker/tests/orm_no_default_value.out
index 43d11d19b5..104496004e 100644
--- a/vlib/v/checker/tests/orm_no_default_value.out
+++ b/vlib/v/checker/tests/orm_no_default_value.out
@@ -1,4 +1,4 @@
-vlib/v/checker/tests/orm_no_default_value.vv:11:4: error: assignment requires a non empty `or {}` block
+vlib/v/checker/tests/orm_no_default_value.vv:11:4: error: expression requires a non empty `or {}` block
     9 |     _ := sql db {
    10 |         select from Person
    11 |     } or {
diff --git a/vlib/v/eval/eval.v b/vlib/v/eval/eval.v
index 8f615be284..726fc9071f 100644
--- a/vlib/v/eval/eval.v
+++ b/vlib/v/eval/eval.v
@@ -276,6 +276,7 @@ pub fn (mut e Eval) register_symbol(stmt ast.Stmt, mod string, file string) {
 	}
 }
 
+@[noreturn]
 fn (e &Eval) error(msg string) {
 	eprintln('> V interpreter backtrace:')
 	e.print_backtrace()
diff --git a/vlib/v/gen/c/if.v b/vlib/v/gen/c/if.v
index 9ae2a07634..295070b598 100644
--- a/vlib/v/gen/c/if.v
+++ b/vlib/v/gen/c/if.v
@@ -188,7 +188,7 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 	// Always use this in -autofree, since ?: can have tmp expressions that have to be freed.
 	needs_tmp_var := g.need_tmp_var_in_if(node)
 	needs_conds_order := g.needs_conds_order(node)
-	tmp := if needs_tmp_var { g.new_tmp_var() } else { '' }
+	tmp := if node.typ != ast.void_type && needs_tmp_var { g.new_tmp_var() } else { '' }
 	mut cur_line := ''
 	mut raw_state := false
 	if needs_tmp_var {
@@ -210,7 +210,9 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 		}
 		cur_line = g.go_before_last_stmt()
 		g.empty_line = true
-		g.writeln('${styp} ${tmp}; /* if prepend */')
+		if tmp != '' {
+			g.writeln('${styp} ${tmp}; /* if prepend */')
+		}
 		if g.infix_left_var_name.len > 0 {
 			g.writeln('if (${g.infix_left_var_name}) {')
 			g.indent++
diff --git a/vlib/v/parser/expr.v b/vlib/v/parser/expr.v
index c9c7450746..044c5495c1 100644
--- a/vlib/v/parser/expr.v
+++ b/vlib/v/parser/expr.v
@@ -787,7 +787,9 @@ fn (mut p Parser) infix_expr(left ast.Expr) ast.Expr {
 
 	right_op_pos := p.tok.pos()
 	old_assign_rhs := p.inside_assign_rhs
-	p.inside_assign_rhs = true
+	if op in [.decl_assign, .assign] {
+		p.inside_assign_rhs = true
+	}
 	right = p.expr(precedence)
 	p.inside_assign_rhs = old_assign_rhs
 	if op in [.plus, .minus, .mul, .div, .mod, .lt, .eq] && mut right is ast.PrefixExpr {
diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index 57eff4bb46..4648d53641 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -872,7 +872,10 @@ fn (mut p Parser) anon_fn() ast.AnonFn {
 	if p.tok.kind == .lcbr {
 		tmp := p.label_names
 		p.label_names = []
+		old_assign_rhs := p.inside_assign_rhs
+		p.inside_assign_rhs = false
 		stmts = p.parse_block_no_scope(false)
+		p.inside_assign_rhs = old_assign_rhs
 		label_names = p.label_names.clone()
 		p.label_names = tmp
 	}
@@ -1164,16 +1167,19 @@ fn (mut p Parser) fn_params() ([]ast.Param, bool, bool, bool) {
 fn (mut p Parser) spawn_expr() ast.SpawnExpr {
 	p.next()
 	spos := p.tok.pos()
+	old_inside_assign_rhs := p.inside_assign_rhs
+	p.inside_assign_rhs = false
 	expr := p.expr(0)
-	call_expr := if expr is ast.CallExpr {
+	p.inside_assign_rhs = old_inside_assign_rhs
+	mut call_expr := if expr is ast.CallExpr {
 		expr
 	} else {
 		p.error_with_pos('expression in `spawn` must be a function call', expr.pos())
 		ast.CallExpr{
-			scope:          p.scope
-			is_return_used: true
+			scope: p.scope
 		}
 	}
+	call_expr.is_return_used = true
 	pos := spos.extend(p.prev_tok.pos())
 	p.register_auto_import('sync.threads')
 	p.table.gostmts++
@@ -1186,16 +1192,19 @@ fn (mut p Parser) spawn_expr() ast.SpawnExpr {
 fn (mut p Parser) go_expr() ast.GoExpr {
 	p.next()
 	spos := p.tok.pos()
+	old_inside_assign_rhs := p.inside_assign_rhs
+	p.inside_assign_rhs = false
 	expr := p.expr(0)
-	call_expr := if expr is ast.CallExpr {
+	p.inside_assign_rhs = old_inside_assign_rhs
+	mut call_expr := if expr is ast.CallExpr {
 		expr
 	} else {
 		p.error_with_pos('expression in `go` must be a function call', expr.pos())
 		ast.CallExpr{
-			scope:          p.scope
-			is_return_used: true
+			scope: p.scope
 		}
 	}
+	call_expr.is_return_used = true
 	pos := spos.extend(p.prev_tok.pos())
 	// p.register_auto_import('coroutines')
 	p.table.gostmts++
diff --git a/vlib/v/parser/if_match.v b/vlib/v/parser/if_match.v
index 7ebc25b119..0327d306f2 100644
--- a/vlib/v/parser/if_match.v
+++ b/vlib/v/parser/if_match.v
@@ -170,13 +170,6 @@ fn (mut p Parser) if_expr(is_comptime bool, is_expr bool) ast.IfExpr {
 		}
 		p.open_scope()
 		stmts := p.parse_block_no_scope(false)
-		// if the last expr is a callexpr mark its return as used
-		if p.inside_assign_rhs && stmts.len > 0 && stmts.last() is ast.ExprStmt {
-			mut last_expr := stmts.last() as ast.ExprStmt
-			if mut last_expr.expr is ast.CallExpr {
-				last_expr.expr.is_return_used = true
-			}
-		}
 		branches << ast.IfBranch{
 			cond:     cond
 			stmts:    stmts
@@ -361,12 +354,6 @@ fn (mut p Parser) match_expr() ast.MatchExpr {
 		pos := branch_first_pos.extend_with_last_line(branch_last_pos, p.prev_tok.line_nr)
 		branch_pos := branch_first_pos.extend_with_last_line(p.tok.pos(), p.tok.line_nr)
 		post_comments := p.eat_comments()
-		if p.inside_assign_rhs && stmts.len > 0 && stmts.last() is ast.ExprStmt {
-			mut last_expr := stmts.last() as ast.ExprStmt
-			if mut last_expr.expr is ast.CallExpr {
-				last_expr.expr.is_return_used = true
-			}
-		}
 		branches << ast.MatchBranch{
 			exprs:         exprs
 			ecmnts:        ecmnts
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 1db20ec8db..22798f4936 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -593,6 +593,8 @@ fn (mut p Parser) parse_block() []ast.Stmt {
 fn (mut p Parser) parse_block_no_scope(is_top_level bool) []ast.Stmt {
 	p.check(.lcbr)
 	mut stmts := []ast.Stmt{cap: 20}
+	old_assign_rhs := p.inside_assign_rhs
+	p.inside_assign_rhs = false
 	if p.tok.kind != .rcbr {
 		mut count := 0
 		for p.tok.kind !in [.eof, .rcbr] {
@@ -608,13 +610,51 @@ fn (mut p Parser) parse_block_no_scope(is_top_level bool) []ast.Stmt {
 			}
 		}
 	}
+	p.inside_assign_rhs = old_assign_rhs
 	if is_top_level {
 		p.top_level_statement_end()
 	}
 	p.check(.rcbr)
+	// on assignment the last callexpr must be marked as return used recursively
+	if p.inside_assign_rhs && stmts.len > 0 {
+		mut last_stmt := stmts.last()
+		p.mark_last_call_return_as_used(mut last_stmt)
+	}
 	return stmts
 }
 
+fn (mut p Parser) mark_last_call_return_as_used(mut last_stmt ast.Stmt) {
+	match mut last_stmt {
+		ast.ExprStmt {
+			match mut last_stmt.expr {
+				ast.CallExpr {
+					// last stmt on block is CallExpr
+					last_stmt.expr.is_return_used = true
+				}
+				ast.IfExpr {
+					// last stmt on block is: if .. { foo() } else { bar() }
+					for mut branch in last_stmt.expr.branches {
+						if branch.stmts.len > 0 {
+							mut last_if_stmt := branch.stmts.last()
+							p.mark_last_call_return_as_used(mut last_if_stmt)
+						}
+					}
+				}
+				ast.ConcatExpr {
+					// last stmt on block is: a, b, c := ret1(), ret2(), ret3()
+					for mut expr in last_stmt.expr.vals {
+						if mut expr is ast.CallExpr {
+							expr.is_return_used = true
+						}
+					}
+				}
+				else {}
+			}
+		}
+		else {}
+	}
+}
+
 fn (mut p Parser) next() {
 	p.prev_tok = p.tok
 	p.tok = p.peek_tok
diff --git a/vlib/v/tests/fns/call_or_empty_block_test.v b/vlib/v/tests/fns/call_or_empty_block_test.v
new file mode 100644
index 0000000000..945eb6d5db
--- /dev/null
+++ b/vlib/v/tests/fns/call_or_empty_block_test.v
@@ -0,0 +1,17 @@
+fn foo() ! {
+}
+
+fn bar() ?int {
+	return 1
+}
+
+fn test_main() {
+	y := if a := bar() {
+		dump(a)
+		foo() or {}
+		true
+	} else {
+		false
+	}
+	assert y
+}
diff --git a/vlib/v/tests/options/option_call_on_orexpr_test.v b/vlib/v/tests/options/option_call_on_orexpr_test.v
index 5a8de2f86a..0e956770d7 100644
--- a/vlib/v/tests/options/option_call_on_orexpr_test.v
+++ b/vlib/v/tests/options/option_call_on_orexpr_test.v
@@ -10,7 +10,7 @@ fn find_startswith_string(a []string, search string) ?string {
 fn find_any_startswith_string(a []string, b []string, search string) ?string {
 	// cannot convert 'struct _option_string' to 'struct string'
 	// V wants the or {} block to return a string, but find_startswith_string returns ?string
-	return find_startswith_string(a, search) or { find_startswith_string(b, search) }
+	return find_startswith_string(a, search) or { find_startswith_string(b, search)? }
 }
 
 fn find_any_startswith_string_unwrapped(a []string, b []string, search string) ?string {
@@ -26,4 +26,10 @@ fn test_main() {
 	var2 := find_any_startswith_string_unwrapped(['foobar', 'barfoo'], ['deadbeef', 'beefdead'],
 		'dead')
 	dump(var2)
+	assert var2 != none
+
+	var3 := find_any_startswith_string_unwrapped(['foobar', 'barfoo'], ['deadbeef', 'beefdead'],
+		'error')
+	dump(var3)
+	assert var3 == none
 }