diff --git a/src/MQTTAsync.c b/src/MQTTAsync.c
index b49f1580..5bda04b9 100644
--- a/src/MQTTAsync.c
+++ b/src/MQTTAsync.c
@@ -804,11 +804,17 @@ int MQTTAsync_connect(MQTTAsync handle, const MQTTAsync_connectOptions* options)
 #endif
 
 	if (m->c->username)
+	{
 		free((void*)m->c->username);
+		m->c->username = NULL;
+	}
 	if (options->username)
 		m->c->username = MQTTStrdup(options->username);
 	if (m->c->password)
+	{
 		free((void*)m->c->password);
+		m->c->password = NULL;
+	}
 	if (options->password)
 	{
 		m->c->password = MQTTStrdup(options->password);
diff --git a/src/MQTTClient.c b/src/MQTTClient.c
index d4ed60e9..406bad91 100644
--- a/src/MQTTClient.c
+++ b/src/MQTTClient.c
@@ -1625,11 +1625,17 @@ static MQTTResponse MQTTClient_connectURI(MQTTClient handle, MQTTClient_connectO
 #endif
 
 	if (m->c->username)
+	{
 		free((void*)m->c->username);
+		m->c->username = NULL;
+	}
 	if (options->username)
 		m->c->username = MQTTStrdup(options->username);
 	if (m->c->password)
+	{
 		free((void*)m->c->password);
+		m->c->password = NULL;
+	}
 	if (options->password)
 	{
 		m->c->password = MQTTStrdup(options->password);