diff --git a/src/diff.c b/src/diff.c
index c001761..0399e79 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -2266,6 +2266,8 @@
 		p += 9;
 		diff_algorithm_new = XDF_HISTOGRAM_DIFF;
 	    }
+	    else
+		return FAIL;
 	}
 
 	if (*p != ',' && *p != NUL)