diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 22b396f371..acdc2a75c6 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3208,8 +3208,13 @@ pub fn (mut c Checker) check_expr_opt_call(expr ast.Expr, ret_type ast.Type) ast
 	if expr is ast.CallExpr {
 		if expr.return_type.has_flag(.optional) {
 			if expr.or_block.kind == .absent {
-				c.error('${expr.name}() returns an option, so it should have either an `or {}` block, or `?` at the end',
-					expr.pos)
+				if c.inside_defer {
+					c.error('${expr.name}() returns an option, so it should have an `or {}` block at the end',
+						expr.pos)
+				} else {
+					c.error('${expr.name}() returns an option, so it should have either an `or {}` block, or `?` at the end',
+						expr.pos)
+				}
 			} else {
 				c.check_or_expr(expr.or_block, ret_type, expr.return_type.clear_flag(.optional))
 			}
diff --git a/vlib/v/checker/tests/defer_optional.out b/vlib/v/checker/tests/defer_optional.out
new file mode 100644
index 0000000000..184e35e641
--- /dev/null
+++ b/vlib/v/checker/tests/defer_optional.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/defer_optional.vv:5:3: error: opt() returns an option, so it should have an `or {}` block at the end
+    3 | fn thing() ?string {
+    4 |     defer {
+    5 |         opt()
+      |         ~~~~~
+    6 |     }
+    7 |     return 'ok'
\ No newline at end of file
diff --git a/vlib/v/checker/tests/defer_optional.vv b/vlib/v/checker/tests/defer_optional.vv
new file mode 100644
index 0000000000..f153430535
--- /dev/null
+++ b/vlib/v/checker/tests/defer_optional.vv
@@ -0,0 +1,8 @@
+fn opt() ? {}
+
+fn thing() ?string {
+	defer {
+		opt()
+	}
+	return 'ok'
+}
\ No newline at end of file
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 1096dc8068..6f2de5a6de 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -4902,7 +4902,9 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 			// `tmp := foo(a, b, c); free(a); free(b); free(c); return tmp;`
 			// Save return value in a temp var so that all args (a,b,c) can be freed
 			// Don't use a tmp var if a variable is simply returned: `return x`
-			if node.exprs[0] !is ast.Ident {
+			// Just in case of defer statements exists, that the return values cannot
+			// be modified.
+			if node.exprs[0] !is ast.Ident || use_tmp_var {
 				g.write('$ret_typ $tmpvar = ')
 			} else {
 				use_tmp_var = false
diff --git a/vlib/v/tests/defer_test.v b/vlib/v/tests/defer_test.v
index 0a2be26913..7bebf11e45 100644
--- a/vlib/v/tests/defer_test.v
+++ b/vlib/v/tests/defer_test.v
@@ -142,3 +142,15 @@ fn test_defer_str_interpol() {
 		t << '${t[0]}'
 	}
 }
+
+fn test_defer_not_change_return_values() {
+	assert num() == 10
+}
+
+fn num() int {
+	mut ret := 10
+	defer {
+		ret = 20
+	}
+	return ret
+}