diff --git a/ext/gd/gd.c b/ext/gd/gd.c
index 76fb2347d28..350a33beb6f 100644
--- a/ext/gd/gd.c
+++ b/ext/gd/gd.c
@@ -876,6 +876,10 @@ PHP_FUNCTION(imagetruecolortopalette)
 	convert_to_boolean_ex(dither);
 	convert_to_long_ex(ncolors);
 
+	if (Z_LVAL_PP(ncolors) <= 0) {
+		php_error_docref(NULL TSRMLS_CC, E_WARNING, "Number of colors has to be greater than zero");
+		RETURN_FALSE;
+	}
 	gdImageTrueColorToPalette(im, Z_LVAL_PP(dither), Z_LVAL_PP(ncolors));
 
 	RETURN_TRUE;