diff --git a/composite.cpp b/composite.cpp
--- a/composite.cpp
+++ b/composite.cpp
@@ -426,6 +426,7 @@
     m_scene = NULL;
     compositeTimer.stop();
     repaints_region = QRegion();
+    m_bufferSwapPending = false;
 
     m_state = State::Off;
     emit compositingToggled(false);
@@ -628,14 +629,15 @@
 
 void Compositor::bufferSwapComplete()
 {
-    assert(m_bufferSwapPending);
     m_bufferSwapPending = false;
 
     emit bufferSwapCompleted();
 
     if (m_composeAtSwapCompletion) {
         m_composeAtSwapCompletion = false;
-        performCompositing();
+        // We start the composite timer here to avoid calling
+        // performCompositing() from the event handler.
+        compositeTimer.start(1, this);
     }
 }