diff --git a/src/adldap/ad_interface.cpp b/src/adldap/ad_interface.cpp
index c473c05c..b3b83cb8 100644
--- a/src/adldap/ad_interface.cpp
+++ b/src/adldap/ad_interface.cpp
@@ -92,6 +92,7 @@ void *AdInterfacePrivate::s_sasl_nocanon = LDAP_OPT_ON;
 int AdInterfacePrivate::s_port = 0;
 CertStrategy AdInterfacePrivate::s_cert_strat = CertStrategy_Never;
 SMBCCTX *AdInterfacePrivate::smbc = NULL;
+QMutex AdInterfacePrivate::mutex;
 
 void get_auth_data_fn(const char *pServer, const char *pShare, char *pWorkgroup, int maxLenWorkgroup, char *pUsername, int maxLenUsername, char *pPassword, int maxLenPassword) {
     UNUSED_ARG(pServer);
@@ -327,7 +328,9 @@ void AdInterface::set_cert_strategy(const CertStrategy strategy) {
 }
 
 AdInterfacePrivate::AdInterfacePrivate(AdInterface *q_arg) {
+    mutex.lock();
     q = q_arg;
+    mutex.unlock();
 }
 
 bool AdInterface::is_connected() const {
diff --git a/src/adldap/ad_interface_p.h b/src/adldap/ad_interface_p.h
index 657927a5..ecfbc3fb 100644
--- a/src/adldap/ad_interface_p.h
+++ b/src/adldap/ad_interface_p.h
@@ -23,6 +23,7 @@
 
 #include <QCoreApplication>
 #include <QList>
+#include <QMutex>
 
 class AdInterface;
 class AdConfig;
@@ -34,6 +35,7 @@ class AdInterfacePrivate {
     Q_DECLARE_TR_FUNCTIONS(AdInterfacePrivate)
 
     friend AdInterface;
+    static QMutex mutex;
 
 public:
     AdInterfacePrivate(AdInterface *q);