diff --git a/coders/webp.c b/coders/webp.c
index d65e6e2..bd26b7a 100644
--- a/coders/webp.c
+++ b/coders/webp.c
@@ -239,12 +239,12 @@
     Open image file.
   */
   assert(image_info != (const ImageInfo *) NULL);
-  assert(image_info->signature == MagickSignature);
+  assert(image_info->signature == MagickCoreSignature);
   if (image_info->debug != MagickFalse)
     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
       image_info->filename);
   assert(exception != (ExceptionInfo *) NULL);
-  assert(exception->signature == MagickSignature);
+  assert(exception->signature == MagickCoreSignature);
   image=AcquireImage(image_info,exception);
   status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
   if (status == MagickFalse)
@@ -531,9 +531,9 @@
     Open output image file.
   */
   assert(image_info != (const ImageInfo *) NULL);
-  assert(image_info->signature == MagickSignature);
+  assert(image_info->signature == MagickCoreSignature);
   assert(image != (Image *) NULL);
-  assert(image->signature == MagickSignature);
+  assert(image->signature == MagickCoreSignature);
   if (image->debug != MagickFalse)
     (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
   if ((image->columns > 16383UL) || (image->rows > 16383UL))