diff --git a/include/znc/Chan.h b/include/znc/Chan.h
index 31fa8e34..831d50ae 100644
--- a/include/znc/Chan.h
+++ b/include/znc/Chan.h
@@ -168,6 +168,7 @@ class CChan : private CCoreTranslationMixin {
     void Enable();
     void IncJoinTries() { m_uJoinTries++; }
     void ResetJoinTries() { m_uJoinTries = 0; }
+    void SetParting(bool b) { m_bParting = b; }
     // !Setters
 
     // Getters
@@ -199,6 +200,7 @@ class CChan : private CCoreTranslationMixin {
     bool HasAutoClearChanBufferSet() const {
         return m_bHasAutoClearChanBufferSet;
     }
+    bool IsParting() const { return m_bParting; }
     // !Getters
   private:
   protected:
@@ -223,6 +225,7 @@ class CChan : private CCoreTranslationMixin {
     CBuffer m_Buffer;
 
     bool m_bModeKnown;
+    bool m_bParting;
     std::map<char, CString> m_mcsModes;
 };
 
diff --git a/src/Chan.cpp b/src/Chan.cpp
index 23f949a8..fd370f2a 100644
--- a/src/Chan.cpp
+++ b/src/Chan.cpp
@@ -30,6 +30,7 @@ CChan::CChan(const CString& sName, CIRCNetwork* pNetwork, bool bInConfig,
              CConfig* pConfig)
     : m_bDetached(false),
       m_bIsOn(false),
+      m_bParting(false),
       m_bAutoClearChanBuffer(pNetwork->GetUser()->AutoClearChanBuffer()),
       m_bInConfig(bInConfig),
       m_bDisabled(false),
@@ -84,6 +85,7 @@ CChan::~CChan() { ClearNicks(); }
 
 void CChan::Reset() {
     m_bIsOn = false;
+    m_bParting = false;
     m_bModeKnown = false;
     m_mcsModes.clear();
     m_sTopic = "";
@@ -143,7 +145,7 @@ void CChan::JoinUser(const CString& sKey) {
     if (!IsOn() && !sKey.empty()) {
         SetKey(sKey);
     }
-    if (m_pNetwork->IsIRCConnected() && !IsOn()) {
+    if (m_pNetwork->IsIRCConnected() && (!IsOn() || IsParting())) {
         m_pNetwork->PutIRC("JOIN " + GetName() + " " + GetKey());
     }
 }
diff --git a/src/Client.cpp b/src/Client.cpp
index f51e8371..a5020dd8 100644
--- a/src/Client.cpp
+++ b/src/Client.cpp
@@ -1469,7 +1469,7 @@ bool CClient::OnJoinMessage(CJoinMessage& Message) {
             if (pChan) {
                 if (pChan->IsDetached())
                     pChan->AttachUser(this);
-                else
+                else if (!pChan->IsOn() || pChan->IsParting())
                     pChan->JoinUser(sKey);
                 continue;
             } else if (!sChannel.empty()) {
@@ -1592,7 +1592,7 @@ bool CClient::OnPartMessage(CPartMessage& Message) {
             PutStatusNotice(t_f("Removing channel {1}")(sChan));
             m_pNetwork->DelChan(sChan);
         } else {
-            if (pChan) pChan->SetIsOn(false);
+            if (pChan) pChan->SetParting(true);
             sChans += (sChans.empty()) ? sChan : CString("," + sChan);
         }
     }
diff --git a/src/IRCSock.cpp b/src/IRCSock.cpp
index 6695b240..82a9fc3e 100644
--- a/src/IRCSock.cpp
+++ b/src/IRCSock.cpp
@@ -692,6 +692,7 @@ bool CIRCSock::OnJoinMessage(CJoinMessage& Message) {
         if (pChan) {
             pChan->Enable();
             pChan->SetIsOn(true);
+            pChan->SetParting(false);
             PutIRC("MODE " + sChan);
         }
     } else {
@@ -727,6 +728,7 @@ bool CIRCSock::OnKickMessage(CKickMessage& Message) {
 
     if (GetNick().Equals(sKickedNick) && pChan) {
         pChan->SetIsOn(false);
+        pChan->SetParting(false);
 
         // Don't try to rejoin!
         pChan->Disable();
@@ -1119,6 +1121,19 @@ bool CIRCSock::OnNumericMessage(CNumericMessage& Message) {
                 m_pNetwork->AddMotdBuffer(BufferMessage(Message));
             }
             break;
+        case 403:  // ERR_NOSUCHCHANNEL
+        case 442:  // ERR_NOTONCHANNEL
+            {
+                CString sChan = Message.GetParam(1);
+                CChan* pChan = m_pNetwork->FindChan(sChan);
+                if (pChan && pChan->IsParting()) {
+                    pChan->SetIsOn(false);
+                    pChan->SetParting(false);
+                    m_pNetwork->PutStatus(
+                        t_f("PART failed for channel {1}")(sChan));
+                }
+            }
+            break;
         case 437:
             // :irc.server.net 437 * badnick :Nick/channel is temporarily unavailable
             // :irc.server.net 437 mynick badnick :Nick/channel is temporarily unavailable
@@ -1189,6 +1204,7 @@ bool CIRCSock::OnPartMessage(CPartMessage& Message) {
     }
 
     if (Nick.NickEquals(GetNick())) {
+        if (pChan) pChan->SetParting(false);
         m_pNetwork->DelChan(sChan);
     }
 
diff --git a/test/IRCSockTest.cpp b/test/IRCSockTest.cpp
index f6d38134..97b6314b 100644
--- a/test/IRCSockTest.cpp
+++ b/test/IRCSockTest.cpp
@@ -558,3 +558,44 @@ TEST_F(IRCSockTest, ChanMode) {
         ":are supported by this server");
 	m_pTestSock->ReadLine(":irc.znc.in 324 me #chan +ntf ");
 }
+
+TEST_F(IRCSockTest, PartingFlag) {
+    // Set channel as joined
+    m_pTestChan->SetIsOn(true);
+
+    CMessage clientPart("PART #chan");
+    m_pTestClient->ReadLine(clientPart.ToString());
+
+    EXPECT_THAT(m_pTestSock->vsLines, ElementsAre("PART #chan"));
+    EXPECT_TRUE(m_pTestChan->IsParting());
+
+    m_pTestSock->Reset();
+
+    CMessage serverPart(":me PART #chan");
+    m_pTestSock->ReadLine(serverPart.ToString());
+
+    // IsParting() should be free
+    EXPECT_FALSE(m_pTestChan->IsParting());
+
+    // Verify channel was deleted
+    EXPECT_EQ(m_pTestNetwork->FindChan("#chan"), nullptr);
+}
+
+TEST_F(IRCSockTest, PartingFlagOnError) {
+    // Set channel as joined
+    m_pTestChan->SetIsOn(true);
+
+    CMessage clientPart("PART #chan");
+    m_pTestClient->ReadLine(clientPart.ToString());
+
+    m_pTestSock->Reset();
+
+    CMessage errorMsg(":server 442 me #chan :You're not on that channel");
+    m_pTestSock->ReadLine(errorMsg.ToString());
+
+    // IsParting() should be free
+    EXPECT_FALSE(m_pTestChan->IsParting());
+
+    // Verify channel was deleted
+    EXPECT_NE(m_pTestNetwork->FindChan("#chan"), nullptr);
+}
\ No newline at end of file
diff --git a/test/integration/tests/core.cpp b/test/integration/tests/core.cpp
index 4169b687..3d8f5a51 100644
--- a/test/integration/tests/core.cpp
+++ b/test/integration/tests/core.cpp
@@ -1318,7 +1318,7 @@ TEST_F(ZNCTest, JoinDetachedChannelMultiClient) {
 
 // Commit ad7bd6d7eed84648638e1b6fd69546b9fe496576
 // prevented rejoining when a client cycles a channel.
-TEST_F(ZNCTest, ClientCycleChannels) {
+TEST_F(ZNCTest, ClientCycleChannel) {
     auto znc = Run();
     auto ircd = ConnectIRCd();
     auto client = LoginClient();
@@ -1333,11 +1333,98 @@ TEST_F(ZNCTest, ClientCycleChannels) {
     client.ReadUntil("End of /NAMES");
 
     // Clients have '/hop' or '/cycle' command that sends
-    // 'PART #channel' and 'JOIN #channel'. Verify ZNC rejoins..
+    // 'PART #channel' and 'JOIN #channel'. Verify ZNC rejoins.
     client.Write(":nick PART #test");
+
+    // Verify PART is forwarded to server
+    QByteArray partMsg;
+    ircd.ReadUntilAndGet("PART", partMsg);
+    EXPECT_THAT(partMsg.toStdString(), HasSubstr("PART #test"));
+
+    ircd.Write(":nick PART #test");
+    client.ReadUntil(":nick PART #test");
+
     client.Write(":nick JOIN #test");
     ircd.ReadUntil("JOIN #test");
 }
 
+TEST_F(ZNCTest, PartWithError403) {
+    auto znc = Run();
+    auto ircd = ConnectIRCd();
+    auto client = LoginClient();
+
+    // Join a channel first
+    client.Write("JOIN #test");
+    client.Close();
+
+    ircd.Write(":server 001 nick :Hello");
+    ircd.ReadUntil("JOIN #test");
+    ircd.Write(":nick JOIN :#test");
+    ircd.Write(":server 353 nick #test :nick");
+    ircd.Write(":server 366 nick #test :End of /NAMES list");
+
+    // Reconnect client and send PART
+    client = LoginClient();
+    client.ReadUntil(":nick JOIN :#test");
+    client.Write("PART #test");
+
+    QByteArray partMsg;
+    ircd.ReadUntilAndGet("PART", partMsg);
+    EXPECT_THAT(partMsg.toStdString(), HasSubstr("PART #test"));
+
+    // Server returns 403 error (ERR_NOSUCHCHANNEL) instead of confirming
+    ircd.Write(":server 403 nick #test :No such channel");
+
+    // Verify client receives the status message about PART failure
+    client.ReadUntil("PART failed for channel #test");
+
+    // Verify channel still exists by trying to rejoin
+    client.Write("JOIN #test");
+    ircd.ReadUntil("JOIN #test");
+    ircd.Write(":nick JOIN :#test");
+    ircd.Write(":server 353 nick #test :nick");
+    ircd.Write(":server 366 nick #test :End of /NAMES list");
+    client.ReadUntil(":nick JOIN :#test");
+}
+
+TEST_F(ZNCTest, PartWithError442) {
+    auto znc = Run();
+    auto ircd = ConnectIRCd();
+    auto client = LoginClient();
+
+    // Join a channel first
+    client.Write("JOIN #test");
+    client.Close();
+
+    ircd.Write(":server 001 nick :Hello");
+    ircd.ReadUntil("JOIN #test");
+    ircd.Write(":nick JOIN :#test");
+    ircd.Write(":server 353 nick #test :nick");
+    ircd.Write(":server 366 nick #test :End of /NAMES list");
+
+    // Reconnect client and send PART
+    client = LoginClient();
+    client.ReadUntil(":nick JOIN :#test");
+    client.Write("PART #test :leaving");
+
+    QByteArray partMsg;
+    ircd.ReadUntilAndGet("PART", partMsg);
+    EXPECT_THAT(partMsg.toStdString(), HasSubstr("PART #test"));
+
+    // Server returns 442 error (ERR_NOTONCHANNEL) instead of confirming
+    ircd.Write(":server 442 nick #test :You're not on that channel");
+
+    // Verify client receives the status message about PART failure
+    client.ReadUntil("PART failed for channel #test");
+
+    // Verify channel still exists by trying to rejoin
+    client.Write("JOIN #test");
+    ircd.ReadUntil("JOIN #test");
+    ircd.Write(":nick JOIN :#test");
+    ircd.Write(":server 353 nick #test :nick");
+    ircd.Write(":server 366 nick #test :End of /NAMES list");
+    client.ReadUntil(":nick JOIN :#test");
+}
+
 }  // namespace
 }  // namespace znc_inttest