diff --git a/src/unix/uiactionx11.cpp b/src/unix/uiactionx11.cpp
index e8b47f7579..50c525b333 100644
--- a/src/unix/uiactionx11.cpp
+++ b/src/unix/uiactionx11.cpp
@@ -106,6 +106,10 @@ bool wxUIActionSimulatorX11Impl::SendButtonEvent(int button, bool isDown)
             return false;
     }
 
+    // Ensure that the event is received by the correct window by processing
+    // all pending events, notably mouse moves.
+    XSync(m_display, False /* don't discard */);
+
     return DoX11Button(xbutton, isDown);
 }