diff --git a/vlib/v/checker/assign.v b/vlib/v/checker/assign.v
index f40c4151a3..b47c9e1dc0 100644
--- a/vlib/v/checker/assign.v
+++ b/vlib/v/checker/assign.v
@@ -139,6 +139,10 @@ fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 				c.error('cannot reassign using range expression on the left side of an assignment',
 					left.pos)
 			}
+		} else if mut left is ast.Ident && node.op == .decl_assign {
+			if left.name in c.global_names {
+				c.note('the global variable named `${left.name}` already exists', left.pos)
+			}
 		}
 		is_blank_ident := left.is_blank_ident()
 		mut left_type := ast.void_type
diff --git a/vlib/v/checker/tests/globals/global_var_redeclare.out b/vlib/v/checker/tests/globals/global_var_redeclare.out
new file mode 100644
index 0000000000..c94c052e7a
--- /dev/null
+++ b/vlib/v/checker/tests/globals/global_var_redeclare.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/globals/global_var_redeclare.vv:4:2: notice: the global variable named `foobar` already exists
+    2 | 
+    3 | fn main() {
+    4 |     foobar := 2
+      |     ~~~~~~
+    5 |     println(foobar)
+    6 | }
diff --git a/vlib/v/checker/tests/globals/global_var_redeclare.vv b/vlib/v/checker/tests/globals/global_var_redeclare.vv
new file mode 100644
index 0000000000..47ce3638af
--- /dev/null
+++ b/vlib/v/checker/tests/globals/global_var_redeclare.vv
@@ -0,0 +1,6 @@
+__global foobar = 1
+
+fn main() {
+	foobar := 2
+	println(foobar)
+}