diff --git a/src/mux/muxedit.c b/src/mux/muxedit.c
index 02c3edec..63e71a0a 100644
--- a/src/mux/muxedit.c
+++ b/src/mux/muxedit.c
@@ -70,6 +70,7 @@ void WebPMuxDelete(WebPMux* mux) {
     err = ChunkAssignData(&chunk, data, copy_data, tag);                       \
     if (err == WEBP_MUX_OK) {                                                  \
       err = ChunkSetHead(&chunk, (LIST));                                      \
+      if (err != WEBP_MUX_OK) ChunkRelease(&chunk);                            \
     }                                                                          \
     return err;                                                                \
   }
diff --git a/src/mux/muxinternal.c b/src/mux/muxinternal.c
index b9ee6717..75b6b416 100644
--- a/src/mux/muxinternal.c
+++ b/src/mux/muxinternal.c
@@ -155,17 +155,18 @@ WebPMuxError ChunkSetHead(WebPChunk* const chunk,
 
 WebPMuxError ChunkAppend(WebPChunk* const chunk,
                          WebPChunk*** const chunk_list) {
+  WebPMuxError err;
   assert(chunk_list != NULL && *chunk_list != NULL);
 
   if (**chunk_list == NULL) {
-    ChunkSetHead(chunk, *chunk_list);
+    err = ChunkSetHead(chunk, *chunk_list);
   } else {
     WebPChunk* last_chunk = **chunk_list;
     while (last_chunk->next_ != NULL) last_chunk = last_chunk->next_;
-    ChunkSetHead(chunk, &last_chunk->next_);
-    *chunk_list = &last_chunk->next_;
+    err = ChunkSetHead(chunk, &last_chunk->next_);
+    if (err == WEBP_MUX_OK) *chunk_list = &last_chunk->next_;
   }
-  return WEBP_MUX_OK;
+  return err;
 }
 
 //------------------------------------------------------------------------------