diff --git a/grep.c b/grep.c
index 1194d35b5d..0dbdc1d007 100644
--- a/grep.c
+++ b/grep.c
@@ -1735,12 +1735,23 @@ void grep_source_init(struct grep_source *gs, enum grep_source_type type,
 	case GREP_SOURCE_FILE:
 		gs->identifier = xstrdup(identifier);
 		break;
+	case GREP_SOURCE_SUBMODULE:
+		if (!identifier) {
+			gs->identifier = NULL;
+			break;
+		}
+		/*
+		 * FALL THROUGH
+		 * If the identifier is non-NULL (in the submodule case) it
+		 * will be a SHA1 that needs to be copied.
+		 */
 	case GREP_SOURCE_SHA1:
 		gs->identifier = xmalloc(20);
 		hashcpy(gs->identifier, identifier);
 		break;
 	case GREP_SOURCE_BUF:
 		gs->identifier = NULL;
+		break;
 	}
 }
 
@@ -1760,6 +1771,7 @@ void grep_source_clear_data(struct grep_source *gs)
 	switch (gs->type) {
 	case GREP_SOURCE_FILE:
 	case GREP_SOURCE_SHA1:
+	case GREP_SOURCE_SUBMODULE:
 		free(gs->buf);
 		gs->buf = NULL;
 		gs->size = 0;
@@ -1831,8 +1843,10 @@ static int grep_source_load(struct grep_source *gs)
 		return grep_source_load_sha1(gs);
 	case GREP_SOURCE_BUF:
 		return gs->buf ? 0 : -1;
+	case GREP_SOURCE_SUBMODULE:
+		break;
 	}
-	die("BUG: invalid grep_source type");
+	die("BUG: invalid grep_source type to load");
 }
 
 void grep_source_load_driver(struct grep_source *gs)
diff --git a/grep.h b/grep.h
index 5856a23e46..267534ca24 100644
--- a/grep.h
+++ b/grep.h
@@ -161,6 +161,7 @@ struct grep_source {
 		GREP_SOURCE_SHA1,
 		GREP_SOURCE_FILE,
 		GREP_SOURCE_BUF,
+		GREP_SOURCE_SUBMODULE,
 	} type;
 	void *identifier;