diff --git a/src/unix/uiactionx11.cpp b/src/unix/uiactionx11.cpp
index fcfd677e1e..efa2d3fc18 100644
--- a/src/unix/uiactionx11.cpp
+++ b/src/unix/uiactionx11.cpp
@@ -16,6 +16,7 @@
 #include "wx/uiaction.h"
 #include "wx/event.h"
 #include "wx/evtloop.h"
+#include "wx/time.h"
 
 #include "wx/private/uiaction.h"
 
@@ -55,17 +56,21 @@ namespace
 class wxXSync
 {
 public:
+    // This constructor is used before simulating mouse move events.
     wxXSync(wxX11Display& display)
         : m_display(display), m_isMotion(true)
     {
+        WaitIfNecessary();
     }
 
-    wxXSync(wxX11Display& display, bool depressed)
+    // This constructor is used before simulating mouse button or key press or
+    // release events. Currently we handle presses and releases in the same
+    // way, so we don't use the "depressed" parameter, but it conveniently
+    // allows us to distinguish this ctor from the one above, so still keep it.
+    wxXSync(wxX11Display& display, bool WXUNUSED(depressed))
         : m_display(display), m_isMotion(false)
     {
-        depressed ? ++ms_numDepressed : --ms_numDepressed;
-
-        wxASSERT_MSG( ms_numDepressed >= 0, "Invalid call to wxXSync() ctor" );
+        WaitIfNecessary();
     }
 
     ~wxXSync()
@@ -74,37 +79,45 @@ public:
 
         if ( m_isMotion )
         {
+            // We need to yield here to let things update in response to
+            // the move, existing tests in wx own test suite rely on this
+            // (i.e. start failing if this wxYield() is removed) and doing
+            // this doesn't seem to result in any harm.
             wxYield();
         }
         else // it's button or key event
         {
-            if ( ms_numDepressed > 0 )
-            {
-                // Do nothing if a key / button is still depressed.
-                return;
-            }
-
-            wxYield();
-            wxMilliSleep(Default_Delay);
+            // Don't do anything here, in particular do not call wxYield()
+            // as dispatching events from inside e.g. KeyDown() call would
+            // be unexpected -- testing code using wxUIActionSimulator
+            // expects such events to be generated by a call to wxYield()
+            // after simulating them and this is how wxMSW works.
         }
+
+        ms_lastEvent = wxGetLocalTimeMillis();
     }
 
 private:
+    void WaitIfNecessary()
+    {
+        // Simulating events too fast results in just losing them somehow, so
+        // ensure that there is some minimal delay between subsequent events.
+        static int MIN_DELAY_BETWEEN_EVENTS = 20;
+        if ( wxGetLocalTimeMillis() < ms_lastEvent + MIN_DELAY_BETWEEN_EVENTS )
+            wxMilliSleep(MIN_DELAY_BETWEEN_EVENTS);
+    }
+
     wxX11Display& m_display;
     const bool    m_isMotion; // false if it's button or key event.
 
-    enum
-    {
-        Default_Delay = 20  // amount of ms to sleep after key/button release.
-    };
-
-    static int ms_numDepressed;
+    // Time of the last simulated event.
+    static wxMilliClock_t ms_lastEvent;
 
     wxDECLARE_NO_COPY_CLASS(wxXSync);
 };
 
-/*static*/
-int wxXSync::ms_numDepressed = 0;
+/* static */
+wxMilliClock_t wxXSync::ms_lastEvent = 0;
 
 // Base class for both available X11 implementations.
 class wxUIActionSimulatorX11Impl : public wxUIActionSimulatorImpl