diff --git a/ext/gd/libgd/gdft.c b/ext/gd/libgd/gdft.c
index 25974528af8..86dd8c3c771 100644
--- a/ext/gd/libgd/gdft.c
+++ b/ext/gd/libgd/gdft.c
@@ -986,7 +986,7 @@ gdImageStringFTEx (gdImage * im, int *brect, int fg, char *fontlist, double ptsi
 					} else {
 						ch = c & 0xFF;	/* don't extend sign */
 					}
-					next++;
+					if (*next) next++;
 				}
 				break;
 			case gdFTEX_Big5: {