diff --git a/diff.c b/diff.c
index cbf25473c..c253015c5 100644
--- a/diff.c
+++ b/diff.c
@@ -1381,6 +1381,7 @@ static struct builtin_funcname_pattern {
 			"[A-Za-z_][A-Za-z_0-9]*\\)\\{2,\\}"
 			"[ 	]*([^;]*\\)$" },
 	{ "tex", "^\\(\\\\\\(sub\\)*section{.*\\)$" },
+	{ "ruby", "^\\s*\\(\\(class\\|module\\|def\\)\\s.*\\)$" },
 };
 
 static const char *diff_funcname_pattern(struct diff_filespec *one)