diff --git a/PDF/src/pngwutil.c b/PDF/src/pngwutil.c
index fef38aef9..64331bb62 100644
--- a/PDF/src/pngwutil.c
+++ b/PDF/src/pngwutil.c
@@ -1313,7 +1313,7 @@ png_check_keyword(png_structp png_ptr, png_charp key, png_charpp new_key)
    if (key_len > 79)
    {
       png_warning(png_ptr, "keyword length must be 1 - 79 characters");
-      new_key[79] = '\0';
+      *new_key[79] = '\0';
       key_len = 79;
    }