diff --git a/src/backend/distributed/utils/connection_cache.c b/src/backend/distributed/utils/connection_cache.c
index 1998d7760..83eb73088 100644
--- a/src/backend/distributed/utils/connection_cache.c
+++ b/src/backend/distributed/utils/connection_cache.c
@@ -192,19 +192,27 @@ PurgeConnection(PGconn *connection)
 
 
 /*
- * SqlStateMatchesCategory returns true if the given sql state is in the given
- * error category. Note that we use ERRCODE_TO_CATEGORY macro to determine error
- * category of the sql state and expect the caller to use the same macro for the
- * error category.
+ * SqlStateMatchesCategory returns true if the given sql state (which may be
+ * NULL if unknown) is in the given error category. Note that we use
+ * ERRCODE_TO_CATEGORY macro to determine error category of the sql state and
+ * expect the caller to use the same macro for the error category.
  */
 bool
 SqlStateMatchesCategory(char *sqlStateString, int category)
 {
 	bool sqlStateMatchesCategory = false;
-	int sqlState = MAKE_SQLSTATE(sqlStateString[0], sqlStateString[1], sqlStateString[2],
-								 sqlStateString[3], sqlStateString[4]);
+	int sqlState = 0;
+	int sqlStateCategory = 0;
 
-	int sqlStateCategory = ERRCODE_TO_CATEGORY(sqlState);
+	if (sqlStateString == NULL)
+	{
+		return false;
+	}
+
+	sqlState = MAKE_SQLSTATE(sqlStateString[0], sqlStateString[1], sqlStateString[2],
+							 sqlStateString[3], sqlStateString[4]);
+
+	sqlStateCategory = ERRCODE_TO_CATEGORY(sqlState);
 	if (sqlStateCategory == category)
 	{
 		sqlStateMatchesCategory = true;