diff --git a/include/wx/wupdlock.h b/include/wx/wupdlock.h
index 8654ef355b..c1ff5f0ad0 100644
--- a/include/wx/wupdlock.h
+++ b/include/wx/wupdlock.h
@@ -21,7 +21,7 @@ class wxWindowUpdateLocker
 public:
     // create an object preventing updates of the given window (which must have
     // a lifetime at least as great as ours)
-    wxWindowUpdateLocker(wxWindow *win) : m_win(win) { win->Freeze(); }
+    explicit wxWindowUpdateLocker(wxWindow *win) : m_win(win) { win->Freeze(); }
 
     // dtor thaws the window to permit updates again
     ~wxWindowUpdateLocker() { m_win->Thaw(); }
diff --git a/interface/wx/wupdlock.h b/interface/wx/wupdlock.h
index 562fbfa0a7..763ac84213 100644
--- a/interface/wx/wupdlock.h
+++ b/interface/wx/wupdlock.h
@@ -40,7 +40,7 @@ public:
         The parameter must be non-@NULL and the window must exist for longer than
         wxWindowUpdateLocker object itself.
     */
-    wxWindowUpdateLocker(wxWindow* win);
+    explicit wxWindowUpdateLocker(wxWindow* win);
 
     /**
         Destructor reenables updates for the window this object is associated with.