1 files changed, 2 insertions, 0 deletions
diff --git a/src/H5HG.c b/src/H5HG.c
index 9042146..ba3e968 100644
--- a/src/H5HG.c
+++ b/src/H5HG.c
@@ -320,6 +320,8 @@ H5HG_alloc (H5F_t *f, H5HG_heap_t *heap, size_t size, unsigned * heap_flags_ptr)
                 break;
     } /* end else */
 
+    HDassert(idx < heap->nused);
+
     /* Check if we need more room to store heap objects */
     if(idx>=heap->nalloc) {
         size_t new_alloc;       /* New allocation number */