diff --git a/pngwutil.c b/pngwutil.c
index 062993a63..8340d382e 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -92,8 +92,10 @@ png_write_chunk_header(png_structp png_ptr, png_uint_32 chunk_name,
 {
    png_byte buf[8];
 
-   png_debug2(0, "Writing %s chunk, length = %lu", chunk_name,
-      (unsigned long)length);
+#ifdef PNG_DEBUG
+   PNG_CSTRING_FROM_CHUNK(buf, chunk_name);
+   png_debug2(0, "Writing %s chunk, length = %lu", buf, (unsigned long)length);
+#endif
 
    if (png_ptr == NULL)
       return;