diff --git a/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java b/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java
index bd3d47554..530bf7b11 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java
@@ -522,6 +522,9 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
         closingStreamReceived = false;
         streamId = null;
 
+        // The connection should not be connected nor marked as such prior calling connectInternal().
+        assert !connected;
+
         try {
             // Perform the actual connection to the XMPP service
             connectInternal();
@@ -537,8 +540,9 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
             throw e;
         }
 
-        // Make note of the fact that we're now connected.
-        connected = true;
+        // If connectInternal() did not throw, then this connection must now be marked as connected.
+        assert connected;
+
         callConnectionConnectedListener();
 
         return this;
diff --git a/smack-core/src/main/java/org/jivesoftware/smack/c2s/ModularXmppClientToServerConnection.java b/smack-core/src/main/java/org/jivesoftware/smack/c2s/ModularXmppClientToServerConnection.java
index b099d49d3..5bc020c46 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/c2s/ModularXmppClientToServerConnection.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/c2s/ModularXmppClientToServerConnection.java
@@ -217,6 +217,7 @@ public final class ModularXmppClientToServerConnection extends AbstractXMPPConne
             @Override
             public void setTransport(XmppClientToServerTransport xmppTransport) {
                 ModularXmppClientToServerConnection.this.activeTransport = xmppTransport;
+                ModularXmppClientToServerConnection.this.connected = true;
             }
 
         };
diff --git a/smack-core/src/main/java/org/jivesoftware/smack/c2s/internal/ModularXmppClientToServerConnectionInternal.java b/smack-core/src/main/java/org/jivesoftware/smack/c2s/internal/ModularXmppClientToServerConnectionInternal.java
index 79c0d3d8c..0462307c1 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/c2s/internal/ModularXmppClientToServerConnectionInternal.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/c2s/internal/ModularXmppClientToServerConnectionInternal.java
@@ -116,5 +116,11 @@ public abstract class ModularXmppClientToServerConnectionInternal {
 
     public abstract void setCompressionEnabled(boolean compressionEnabled);
 
+    /**
+     * Set the active transport (TCP, BOSH, WebSocket, …) to be used for the XMPP connection. Also marks the connection
+     * as connected.
+     *
+     * @param xmppTransport the active transport.
+     */
     public abstract void setTransport(XmppClientToServerTransport xmppTransport);
 }
diff --git a/smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java b/smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java
index 2dbb44a04..4e5ff2974 100644
--- a/smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java
+++ b/smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java
@@ -836,6 +836,8 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
         // there is an error establishing the connection
         connectUsingConfiguration();
 
+        connected = true;
+
         // We connected successfully to the servers TCP port
         initConnection();