diff --git a/coders/webp.c b/coders/webp.c
index d25cfc9..48688f8 100644
--- a/coders/webp.c
+++ b/coders/webp.c
@@ -356,7 +356,7 @@
assert(image->signature == MagickSignature);
if (image->debug != MagickFalse)
(void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
- if ((image->columns > 16383) || (image->rows > 16383))
+ if ((image->columns > 16383UL) || (image->rows > 16383UL))
ThrowWriterException(ImageError,"WidthOrHeightExceedsLimit");
status=OpenBlob(image_info,image,WriteBinaryBlobMode,exception);
if (status == MagickFalse)
