diff --git a/magick/blob.c b/magick/blob.c
index 5c0073b..8f0224b 100644
--- a/magick/blob.c
+++ b/magick/blob.c
@@ -3418,7 +3418,7 @@
       break;
     case FileStream:
     {
-      if (fseek(image->blob->file,offset,whence) < 0)
+      if (fseek(image->blob->file,(long) offset,whence) < 0)
         return(-1);
       image->blob->offset=TellBlob(image);
       break;