diff --git a/codegen.c b/codegen.c
index 9015600..92b60be 100644
--- a/codegen.c
+++ b/codegen.c
@@ -347,7 +347,9 @@ void gen(Node *node) {
       printf(".Lend%d:\n", seq);
       printf("  push rax\n");
 
-      truncate(node->ty);
+      if (node->ty->kind != TY_VOID) {
+        truncate(node->ty);
+      }
       return;
     }
     case ND_RETURN:
diff --git a/tests b/tests
index a211ff2..35028df 100644
--- a/tests
+++ b/tests
@@ -62,6 +62,8 @@ int count() {
 
 int param_decay(int x[]) { return 0[x]; }
 
+void voidfn() {}
+
 int main() {
   assert(8, ({
            int a = 3;
@@ -808,6 +810,8 @@ int main() {
   assert(4, ({ struct T *foo; struct T {int x;}; sizeof(struct T); }), "struct T *foo; struct T {int x;}; sizeof(struct T);");
   assert(1, ({ struct T { struct T *next; int x; } a; struct T b; b.x=1; a.next=&b; a.next->x; }), "struct T { struct T *next; int x; } a; struct T b; b.x=1; a.next=&b; a.next->x;");
 
+  voidfn();
+
   printf("OK\n");
   return 0;
 }