diff --git a/contrib/libtests/pngvalid.c b/contrib/libtests/pngvalid.c
index 27e62d176..be545f4d9 100644
--- a/contrib/libtests/pngvalid.c
+++ b/contrib/libtests/pngvalid.c
@@ -1,7 +1,7 @@
 
 /* pngvalid.c - validate libpng by constructing then reading png files.
  *
- * Last changed in libpng 1.5.25 [RDATE%]
+ * Last changed in libpng 1.5.25 [%RDATE%]
  * Copyright (c) 2014-2015 Glenn Randers-Pehrson
  * Written by John Cunningham Bowler
  *