--- a/tools/gfxconv.c	Mon May 14 04:11:31 2018 +0300
+++ b/tools/gfxconv.c	Mon May 14 04:11:45 2018 +0300
@@ -1057,10 +1057,15 @@
     int res = DMERR_OK;
     DMGrowBuf buf;
 
+    dmGrowBufInit(&buf);
+
     // Encode to target format
     dmMsg(1, "Encoding C64 bitmap data to format '%s'\n", fmt->name);
     if ((res = dmC64EncodeBMP(&buf, image, fmt)) != DMERR_OK)
+    {
+        dmErrorMsg("Error encoding bitmap data: %s\n", dmErrorStr(res));
         goto error;
+    }
 
     // And output the file
     dmMsg(1, "Writing output file '%s'\n", filename);