diff --git a/src/librbd/internal.cc b/src/librbd/internal.cc
index b394ddbcda8..28e1d51e110 100644
--- a/src/librbd/internal.cc
+++ b/src/librbd/internal.cc
@@ -1911,7 +1911,7 @@ reprotect_and_return_err:
     ldout(ictx->cct, 20) << "finished flattening" << dendl;
 
   err:
-    delete buf;
+    delete[] buf;
     return r;
   }