diff --git a/coders/json.c b/coders/json.c
index d1460b8..ab32137 100644
--- a/coders/json.c
+++ b/coders/json.c
@@ -653,7 +653,7 @@
       if (j < (MaximumNumberOfPerceptualHashes-1))
         n+=FormatLocaleFile(file,",\n");
     }
-    if (i < (GetPixelChannels(image)-1))
+    if (i < (ssize_t) (GetPixelChannels(image)-1))
       n+=FormatLocaleFile(file,"\n      },\n");
   }
   n+=FormatLocaleFile(file,"\n      }\n");