diff --git a/coders/hrz.c b/coders/hrz.c
index 91b2f67..a596898 100644
--- a/coders/hrz.c
+++ b/coders/hrz.c
@@ -299,6 +299,8 @@
   assert(image->signature == MagickSignature);
   if (image->debug != MagickFalse)
     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
+  assert(exception != (ExceptionInfo *) NULL);
+  assert(exception->signature == MagickSignature);
   status=OpenBlob(image_info,image,WriteBinaryBlobMode,exception);
   if (status == MagickFalse)
     return(status);