diff --git a/gc.c b/gc.c
index f6201c07..8f2cea3f 100644
--- a/gc.c
+++ b/gc.c
@@ -139,6 +139,7 @@ void *gc_try_alloc(gc_heap *h, size_t size)
         } else { /* Take the whole chunk */
           f1->next = f2->next;
         }
+        pthread_mutex_unlock(&heap_lock);
         return f2;
       }
     }