diff --git a/pngwutil.c b/pngwutil.c
index fcc7eb0..22f7797 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1,12 +1,12 @@
 
 /* pngwutil.c - utilities to write a PNG file
  *
- * libpng 0.99
+ * libpng 0.99a
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
  * Copyright (c) 1996, 1997 Andreas Dilger
  * Copyright (c) 1998, Glenn Randers-Pehrson
- * January 30, 1998
+ * January 31, 1998
  */
 
 #define PNG_INTERNAL
@@ -599,7 +599,7 @@
    if (key == NULL || (key_len = png_strlen(key)) == 0)
    {
       png_chunk_warning(png_ptr, "zero length keyword");
-      return 0;
+      return ((png_size_t)0);
    }
 
    png_debug1(2, "Keyword to be checked is '%s'\n", key);
@@ -688,7 +688,7 @@
       key_len = 79;
    }
 
-   return key_len;
+   return (key_len);
 }
 #endif