diff --git a/vlib/builtin/map_test.v b/vlib/builtin/map_test.v
index a265e2bc99..f68fa5391a 100644
--- a/vlib/builtin/map_test.v
+++ b/vlib/builtin/map_test.v
@@ -301,3 +301,15 @@ fn test_map_keys_to_array() {
 	println(sarr)
 	assert sarr == "['a', 'c']"
 }
+
+fn map_in_mut(mut m map[string]int) {
+	if 'one' in m {
+		m['one'] = 2
+	}
+}
+
+fn test_map_in_mut() {
+	mut m := {'one': 1}
+	map_in_mut(mut m)
+	assert m['one'] == 2
+}
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 7a1eceebe9..5103040609 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -1912,6 +1912,9 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 			g.write('_IN_MAP(')
 			g.expr(node.left)
 			g.write(', ')
+			if node.right_type.is_ptr() {
+				g.write('*')
+			}
 			g.expr(node.right)
 			g.write(')')
 		} else if right_sym.kind == .string {