diff --git a/compiler/parser.v b/compiler/parser.v
index 279ef39684..bd24f5a038 100644
--- a/compiler/parser.v
+++ b/compiler/parser.v
@@ -1018,6 +1018,9 @@ fn (p mut Parser) close_scope() {
 			if v.typ.starts_with('array_') { 
 				p.genln('v_array_free($v.name); // close_scope free') 
 			} 
+			else if v.typ == 'string' { 
+				p.genln('v_string_free($v.name); // close_scope free') 
+			} 
 			else { 
 				p.genln('free($v.name); // close_scope free') 
 			} 
@@ -1839,6 +1842,7 @@ fn (p mut Parser) index_expr(typ string, fn_ph int) string {
 			p.gen(']/*r$typ $v.is_mut*/')
 		}
 	}
+	// TODO move this from index_expr() 
 	// TODO if p.tok in ...
 	// if p.tok in [.assign, .plus_assign, .minus_assign]
 	if p.tok == .assign || p.tok == .plus_assign || p.tok == .minus_assign ||
@@ -2335,6 +2339,7 @@ fn (p mut Parser) string_expr() {
 		return
 	}
 	// tmp := p.get_tmp()
+	p.is_alloc = true // $ interpolation means there's allocation 
 	mut args := '"'
 	mut format := '"'
 	p.fgen('\'') 
diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index dbf16b88b5..632ad32c18 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -4,7 +4,6 @@
 
 module builtin
 
-// V strings are not null-terminated.
 struct string {
 mut:
 	hash_cache int 
@@ -25,7 +24,8 @@ fn C.strlen(s byteptr) int
 
 fn todo() { } 
 
-// Converts a C string to a V string
+// Converts a C string to a V string. 
+// String data is reused, not copied. 
 pub fn tos(s byteptr, len int) string {
 	// This should never happen.
 	if isnil(s) {
@@ -48,6 +48,7 @@ pub fn tos_clone(s byteptr) string {
 }
 
 // Same as `tos`, but calculates the length. Called by `string(bytes)` casts. 
+// Used only internally. 
 fn tos2(s byteptr) string {
 	if isnil(s) {
 		panic('tos2: nil string')
@@ -730,7 +731,7 @@ pub fn (c byte) is_letter() bool {
 }
 
 pub fn (s string) free() {
-	C.free(s.str)
+	free(s.str)
 }
 
 /*