diff --git a/ext/gd/libgd/gdparttopng.c b/ext/gd/libgd/gdparttopng.c
index 677a0b57101..a82925b0ed4 100644
--- a/ext/gd/libgd/gdparttopng.c
+++ b/ext/gd/libgd/gdparttopng.c
@@ -37,7 +37,7 @@ main (int argc, char **argv)
   fclose (in);
   if (!im)
     {
-      fprintf (stderr, "Input is not in PNG format!\n");
+      fprintf (stderr, "Input is not in GD2 format!\n");
       exit (1);
     }
   out = fopen (argv[2], "wb");
diff --git a/ext/gd/libgd/gdtopng.c b/ext/gd/libgd/gdtopng.c
index 9de34990ab0..9670b101976 100644
--- a/ext/gd/libgd/gdtopng.c
+++ b/ext/gd/libgd/gdtopng.c
@@ -26,7 +26,7 @@ main (int argc, char **argv)
   fclose (in);
   if (!im)
     {
-      fprintf (stderr, "Input is not in PNG format!\n");
+      fprintf (stderr, "Input is not in GD format!\n");
       exit (1);
     }
   out = fopen (argv[2], "wb");