diff --git a/src/os2/app.cpp b/src/os2/app.cpp
index f6b538d15a..31c1d49629 100644
--- a/src/os2/app.cpp
+++ b/src/os2/app.cpp
@@ -9,6 +9,10 @@
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 
+#ifdef __GNUG__
+    #pragma implementation "app.h"
+#endif
+
 // For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
diff --git a/src/os2/dc.cpp b/src/os2/dc.cpp
index 28ac299e82..4a5cef4e16 100644
--- a/src/os2/dc.cpp
+++ b/src/os2/dc.cpp
@@ -24,6 +24,9 @@
     #include "wx/icon.h"
     #include "wx/msgdlg.h"
     #include "wx/module.h"
+#if wxUSE_STATUSBAR
+    #include "wx/statusbr.h"
+#endif
 #endif
 
 #include "wx/dcprint.h"
diff --git a/src/os2/pen.cpp b/src/os2/pen.cpp
index b26c80e4ab..975a8f96f6 100644
--- a/src/os2/pen.cpp
+++ b/src/os2/pen.cpp
@@ -108,6 +108,10 @@ wxPen::wxPen(
         wxThePenList->AddPen(this);
 } // end of wxPen::wxPen
 
+int wx2os2PenStyle(
+  int                               nWxStyle
+);
+
 bool wxPen::RealizeResource()
 {
     BOOL                            bOk;
diff --git a/src/os2/timer.cpp b/src/os2/timer.cpp
index bb897e1f78..f102ace512 100644
--- a/src/os2/timer.cpp
+++ b/src/os2/timer.cpp
@@ -9,6 +9,10 @@
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 
+#ifdef __GNUG__
+    #pragma implementation "timer.h"
+#endif
+
 // For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
@@ -51,8 +55,8 @@ void wxTimer::Init()
 
 wxTimer::~wxTimer()
 {
-    Stop();
     wxTimer::Stop();
+
     wxTimerList.DeleteObject(this);
 }
 
@@ -164,8 +168,8 @@ ULONG wxTimerProc(
     wxNode*                         pNode = wxTimerList.Find((ULONG)nIdTimer);
 
     wxCHECK_MSG(pNode, 0, wxT("bogus timer id in wxTimerProc") );
-
-    wxProcessTimer(*(wxTimer *)pNode->Data());
+    if (pNode)
+      wxProcessTimer(*(wxTimer *)pNode->Data());
     return 0;
 }
 
diff --git a/src/os2/toolbar.cpp b/src/os2/toolbar.cpp
index 7975660d48..e432c1b1c6 100644
--- a/src/os2/toolbar.cpp
+++ b/src/os2/toolbar.cpp
@@ -17,6 +17,8 @@
 #ifndef WX_PRECOMP
     #include "wx/settings.h"
     #include "wx/window.h"
+    #include "wx/frame.h"
+    #include "wx/app.h"
     #include "wx/dcclient.h"
     #include "wx/dcmemory.h"
 #endif
diff --git a/src/os2/toplevel.cpp b/src/os2/toplevel.cpp
index 834fe8af40..badfc61835 100644
--- a/src/os2/toplevel.cpp
+++ b/src/os2/toplevel.cpp
@@ -36,6 +36,7 @@
     #include "wx/intl.h"
     #include "wx/frame.h"
     #include "wx/control.h"
+    #include "wx/containr.h"        // wxSetFocusToChild()
 #endif //WX_PRECOMP
 
 #include "wx/os2/private.h"
diff --git a/src/os2/window.cpp b/src/os2/window.cpp
index 87e89399f7..85f6f74323 100644
--- a/src/os2/window.cpp
+++ b/src/os2/window.cpp
@@ -35,6 +35,7 @@
     #include "wx/scrolwin.h"
     #include "wx/radiobox.h"
     #include "wx/slider.h"
+    #include "wx/statbox.h"
     #include "wx/statusbr.h"
     #include "wx/toolbar.h"
     #include "wx/settings.h"
@@ -2932,7 +2933,7 @@ MRESULT wxWindowOS2::OS2WindowProc(
             if ( bProcessed )
             {
                 // we never set focus from here
-                mResult = FALSE;
+                mResult = (MRESULT)FALSE;
             }
             break;