diff --git a/src/unix/loop.c b/src/unix/loop.c
index bc45519a..52c9328e 100644
--- a/src/unix/loop.c
+++ b/src/unix/loop.c
@@ -90,7 +90,7 @@ uv_loop_t* uv_loop_new(void) {
 void uv_loop_delete(uv_loop_t* loop) {
   uv_loop_t* default_loop;
   default_loop = default_loop_ptr;
-  uv_loop_close(loop);
+  assert(uv_loop_close(loop) == 0);
   if (loop != default_loop)
     free(loop);
 }
diff --git a/src/win/core.c b/src/win/core.c
index 7e3395bd..2e702768 100644
--- a/src/win/core.c
+++ b/src/win/core.c
@@ -222,7 +222,7 @@ uv_loop_t* uv_loop_new(void) {
 
 
 void uv_loop_delete(uv_loop_t* loop) {
-  uv_loop_close(loop);
+  assert(uv_loop_close(loop) == 0);
   if (loop != &uv_default_loop_)
     free(loop);
 }