diff --git a/src/gtk/app.cpp b/src/gtk/app.cpp
index e7345fe6a9..e29797d061 100644
--- a/src/gtk/app.cpp
+++ b/src/gtk/app.cpp
@@ -82,6 +82,14 @@ void wxExit()
 
 bool wxYield()
 {
+#if wxUSE_THREADS
+    if ( !wxThread::IsMain() )
+    {
+        // can't call gtk_main_iteration() from other threads like this
+        return TRUE;
+    }
+#endif // wxUSE_THREADS
+
 #ifdef __WXDEBUG__
     static bool s_inYield = FALSE;
     
diff --git a/src/gtk1/app.cpp b/src/gtk1/app.cpp
index e7345fe6a9..e29797d061 100644
--- a/src/gtk1/app.cpp
+++ b/src/gtk1/app.cpp
@@ -82,6 +82,14 @@ void wxExit()
 
 bool wxYield()
 {
+#if wxUSE_THREADS
+    if ( !wxThread::IsMain() )
+    {
+        // can't call gtk_main_iteration() from other threads like this
+        return TRUE;
+    }
+#endif // wxUSE_THREADS
+
 #ifdef __WXDEBUG__
     static bool s_inYield = FALSE;