diff --git a/wand/montage.c b/wand/montage.c
index 33f3219..bf98df2 100644
--- a/wand/montage.c
+++ b/wand/montage.c
@@ -407,8 +407,8 @@
(void) InterpretImageFilename(image_info,(Image *) NULL,
image_info->filename,(int) scene,filename);
if (LocaleCompare(filename,image_info->filename) == 0)
- (void) FormatMagickString(filename,MaxTextExtent,"%s.%lu",
- image_info->filename,(unsigned long) scene);
+ (void) FormatMagickString(filename,MaxTextExtent,"%s.%.20g",
+ image_info->filename,(double) scene);
(void) CopyMagickString(image_info->filename,filename,
MaxTextExtent);
}