diff --git a/Documentation/git-remote-helpers.txt b/Documentation/git-remote-helpers.txt
index 5cfdc0cfc5..20a05fe9d8 100644
--- a/Documentation/git-remote-helpers.txt
+++ b/Documentation/git-remote-helpers.txt
@@ -25,7 +25,10 @@ Commands are given by the caller on the helper's standard input, one per line.
 
 'capabilities'::
 	Lists the capabilities of the helper, one per line, ending
-	with a blank line.
+	with a blank line. Each capability may be preceeded with '*'.
+	This marks them mandatory for git version using the remote
+	helper to understand (unknown mandatory capability is fatal
+	error).
 
 'list'::
 	Lists the refs, one per line, in the format "<value> <name>
diff --git a/transport-helper.c b/transport-helper.c
index a721dc25be..4b17aaa237 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -93,25 +93,38 @@ static struct child_process *get_helper(struct transport *transport)
 
 	data->out = xfdopen(helper->out, "r");
 	while (1) {
+		const char *capname;
+		int mandatory = 0;
 		recvline(data, &buf);
 
 		if (!*buf.buf)
 			break;
+
+		if (*buf.buf == '*') {
+			capname = buf.buf + 1;
+			mandatory = 1;
+		} else
+			capname = buf.buf;
+
 		if (debug)
-			fprintf(stderr, "Debug: Got cap %s\n", buf.buf);
-		if (!strcmp(buf.buf, "fetch"))
+			fprintf(stderr, "Debug: Got cap %s\n", capname);
+		if (!strcmp(capname, "fetch"))
 			data->fetch = 1;
-		if (!strcmp(buf.buf, "option"))
+		else if (!strcmp(capname, "option"))
 			data->option = 1;
-		if (!strcmp(buf.buf, "push"))
+		else if (!strcmp(capname, "push"))
 			data->push = 1;
-		if (!strcmp(buf.buf, "import"))
+		else if (!strcmp(capname, "import"))
 			data->import = 1;
-		if (!data->refspecs && !prefixcmp(buf.buf, "refspec ")) {
+		else if (!data->refspecs && !prefixcmp(capname, "refspec ")) {
 			ALLOC_GROW(refspecs,
 				   refspec_nr + 1,
 				   refspec_alloc);
 			refspecs[refspec_nr++] = strdup(buf.buf + strlen("refspec "));
+		} else if (mandatory) {
+			die("Unknown madatory capability %s. This remote "
+			    "helper probably needs newer version of Git.\n",
+			    capname);
 		}
 	}
 	if (refspecs) {