diff --git a/src/os2/fontutil.cpp b/src/os2/fontutil.cpp
index 5f135b0327..a3444c5765 100644
--- a/src/os2/fontutil.cpp
+++ b/src/os2/fontutil.cpp
@@ -17,6 +17,10 @@
 // headers
 // ----------------------------------------------------------------------------
 
+#ifdef __GNUG__
+    #pragma implementation "fontutil.h"
+#endif
+
 // For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
diff --git a/src/os2/iniconf.cpp b/src/os2/iniconf.cpp
index 3b49835c8a..68a8bab6ae 100644
--- a/src/os2/iniconf.cpp
+++ b/src/os2/iniconf.cpp
@@ -63,7 +63,7 @@ wxIniConfig::wxIniConfig(const wxString& strAppName,
 
     // append the extension if none given and it's not an absolute file name
     // (otherwise we assume that they know what they're doing)
-    if ( !wxIsPathSeparator(m_strLocalFilename[0u]) &&
+    if ( !wxIsPathSeparator(m_strLocalFilename[(size_t) 0]) &&
         m_strLocalFilename.Find('.') == wxNOT_FOUND )
     {
         m_strLocalFilename << ".ini";
@@ -88,7 +88,7 @@ void wxIniConfig::SetPath(const wxString& strPath)
   if ( strPath.IsEmpty() ) {
     // nothing
   }
-  else if ( strPath[0u] == wxCONFIG_PATH_SEPARATOR ) {
+  else if ( strPath[(size_t) 0] == wxCONFIG_PATH_SEPARATOR ) {
     // absolute path
     wxSplitPath(aParts, strPath);
   }
@@ -107,7 +107,7 @@ void wxIniConfig::SetPath(const wxString& strPath)
   }
   else {
     // translate
-    m_strGroup = aParts[0u];
+    m_strGroup = aParts[(size_t) 0];
     for ( size_t nPart = 1; nPart < nPartsCount; nPart++ ) {
       if ( nPart > 1 )
         m_strPath << PATH_SEP_REPLACE;
diff --git a/src/os2/menu.cpp b/src/os2/menu.cpp
index 129f2e8d91..442525a8f6 100644
--- a/src/os2/menu.cpp
+++ b/src/os2/menu.cpp
@@ -9,6 +9,10 @@
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 
+#ifdef __GNUG__
+    #pragma implementation "menu.h"
+#endif
+
 // For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
diff --git a/src/os2/mimetype.cpp b/src/os2/mimetype.cpp
index bee950fe6d..28ba45db1f 100644
--- a/src/os2/mimetype.cpp
+++ b/src/os2/mimetype.cpp
@@ -318,7 +318,7 @@ wxMimeTypesManagerImpl::GetFileTypeFromExtension(const wxString& ext)
 {
     // add the leading point if necessary
     wxString str;
-    if ( ext[0u] != wxT('.') ) {
+    if ( ext[(size_t) 0] != wxT('.') ) {
         str = wxT('.');
     }
     str << ext;