diff --git a/magick/coder.h b/magick/coder.h
index b4ad19f..0c831a4 100644
--- a/magick/coder.h
+++ b/magick/coder.h
@@ -37,16 +37,16 @@
     *previous,
     *next;  /* deprecated, use GetCoderInfoList() */
 
-  unsigned long
+  size_t
     signature;
 } CoderInfo;
 
 extern MagickExport char
-  **GetCoderList(const char *,unsigned long *,ExceptionInfo *);
+  **GetCoderList(const char *,size_t *,ExceptionInfo *);
 
 extern MagickExport const CoderInfo
   *GetCoderInfo(const char *,ExceptionInfo *),
-  **GetCoderInfoList(const char *,unsigned long *,ExceptionInfo *);
+  **GetCoderInfoList(const char *,size_t *,ExceptionInfo *);
 
 extern MagickExport MagickBooleanType
   CoderComponentGenesis(void),