diff --git a/src/core/scheduler.cpp b/src/core/scheduler.cpp
--- a/src/core/scheduler.cpp
+++ b/src/core/scheduler.cpp
@@ -129,6 +129,11 @@
     return false;
 }
 
+void SlaveKeeper::clear()
+{
+    m_idleSlaves.clear();
+}
+
 QList<Slave *> SlaveKeeper::allSlaves() const
 {
     return m_idleSlaves.values();
@@ -404,7 +409,11 @@
 
 ProtoQueue::~ProtoQueue()
 {
-    Q_FOREACH (Slave *slave, allSlaves()) {
+    // Gather list of all slaves first
+    const QList<Slave *> slaves = allSlaves();
+    // Clear the idle slaves in the keeper to avoid dangling pointers
+    m_slaveKeeper.clear();
+    for (Slave *slave : slaves) {
         // kill the slave process, then remove the interface in our process
         slave->kill();
         slave->deref();
@@ -1123,7 +1132,9 @@
         m_slaveOnHold = nullptr;
         m_urlOnHold.clear();
     }
-    slave->deref(); // Delete slave
+    // can't use slave->deref() here because we need to use deleteLater
+    slave->aboutToDelete();
+    slave->deleteLater();
 }
 
 void SchedulerPrivate::putSlaveOnHold(KIO::SimpleJob *job, const QUrl &url)
diff --git a/src/core/scheduler_p.h b/src/core/scheduler_p.h
--- a/src/core/scheduler_p.h
+++ b/src/core/scheduler_p.h
@@ -25,6 +25,7 @@
 namespace KIO
 {
 
+// The slave keeper manages the list of idle slaves that can be reused
 class SlaveKeeper : public QObject
 {
     Q_OBJECT
@@ -37,6 +38,8 @@
     KIO::Slave *takeSlaveForJob(KIO::SimpleJob *job);
     // remove slave from keeper
     bool removeSlave(KIO::Slave *slave);
+    // remove all slaves from keeper
+    void clear();
     QList<KIO::Slave *> allSlaves() const;
 
 private:
diff --git a/src/core/slave.h b/src/core/slave.h
--- a/src/core/slave.h
+++ b/src/core/slave.h
@@ -229,6 +229,7 @@
 
     void ref();
     void deref();
+    void aboutToDelete();
 
 public Q_SLOTS:
     void accept();
diff --git a/src/core/slave.cpp b/src/core/slave.cpp
--- a/src/core/slave.cpp
+++ b/src/core/slave.cpp
@@ -298,12 +298,18 @@
     Q_D(Slave);
     d->m_refCount--;
     if (!d->m_refCount) {
-        d->connection->disconnect(this);
-        this->disconnect();
-        deleteLater();
+        aboutToDelete();
+        delete this; // yes it reads funny, but it's too late for a deleteLater() here, no event loop anymore
     }
 }
 
+void Slave::aboutToDelete()
+{
+    Q_D(Slave);
+    d->connection->disconnect(this);
+    this->disconnect();
+}
+
 int Slave::idleTime()
 {
     Q_D(Slave);