diff --git a/src/redis.c b/src/redis.c
index 1f51f288..aa434cac 100644
--- a/src/redis.c
+++ b/src/redis.c
@@ -1083,6 +1083,8 @@ void createSharedObjects(void) {
         "-MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.\r\n"));
     shared.roslaveerr = createObject(REDIS_STRING,sdsnew(
         "-READONLY You can't write against a read only slave.\r\n"));
+    shared.noautherr = createObject(REDIS_STRING,sdsnew(
+        "-NOAUTH Authentication required.\r\n"));
     shared.oomerr = createObject(REDIS_STRING,sdsnew(
         "-OOM command not allowed when used memory > 'maxmemory'.\r\n"));
     shared.execaborterr = createObject(REDIS_STRING,sdsnew(
@@ -1650,7 +1652,7 @@ int processCommand(redisClient *c) {
     if (server.requirepass && !c->authenticated && c->cmd->proc != authCommand)
     {
         flagTransaction(c);
-        addReplyError(c,"operation not permitted");
+        addReply(c,shared.noautherr);
         return REDIS_OK;
     }
 
diff --git a/src/redis.h b/src/redis.h
index e460148d..093c7024 100644
--- a/src/redis.h
+++ b/src/redis.h
@@ -448,7 +448,7 @@ struct sharedObjectsStruct {
     *colon, *nullbulk, *nullmultibulk, *queued,
     *emptymultibulk, *wrongtypeerr, *nokeyerr, *syntaxerr, *sameobjecterr,
     *outofrangeerr, *noscripterr, *loadingerr, *slowscripterr, *bgsaveerr,
-    *masterdownerr, *roslaveerr, *execaborterr,
+    *masterdownerr, *roslaveerr, *execaborterr, *noautherr,
     *oomerr, *plus, *messagebulk, *pmessagebulk, *subscribebulk,
     *unsubscribebulk, *psubscribebulk, *punsubscribebulk, *del, *rpop, *lpop,
     *lpush,
diff --git a/tests/support/server.tcl b/tests/support/server.tcl
index acbfe73c..e10c350f 100644
--- a/tests/support/server.tcl
+++ b/tests/support/server.tcl
@@ -84,8 +84,8 @@ proc ping_server {host port} {
         puts $fd "PING\r\n"
         flush $fd
         set reply [gets $fd]
-        if {[string range $reply 0 4] eq {+PONG} ||
-            [string range $reply 0 3] eq {-ERR}} {
+        if {[string range $reply 0 0] eq {+} ||
+            [string range $reply 0 0] eq {-}} {
             set retval 1
         }
         close $fd
diff --git a/tests/unit/auth.tcl b/tests/unit/auth.tcl
index bd4b8dca..15753e9e 100644
--- a/tests/unit/auth.tcl
+++ b/tests/unit/auth.tcl
@@ -14,7 +14,7 @@ start_server {tags {"auth"} overrides {requirepass foobar}} {
     test {Arbitrary command gives an error when AUTH is required} {
         catch {r set foo bar} err
         set _ $err
-    } {ERR*operation not permitted}
+    } {NOAUTH*}
 
     test {AUTH succeeds when the right password is given} {
         r auth foobar