diff --git a/writerfilter/source/dmapper/ConversionHelper.cxx b/writerfilter/source/dmapper/ConversionHelper.cxx
index 40ea9bdc2674..88c93728a5ba 100644
--- a/writerfilter/source/dmapper/ConversionHelper.cxx
+++ b/writerfilter/source/dmapper/ConversionHelper.cxx
@@ -147,6 +147,7 @@ void MakeBorderLine( sal_Int32 nLineThickness,   sal_Int32 nLineType,
     rToFill.Color = nLineColor;
 }
 
+namespace {
 void lcl_SwapQuotesInField(OUString &rFmt)
 {
     //Swap unescaped " and ' with ' and "
@@ -172,6 +173,7 @@ bool lcl_IsNotAM(OUString& rFmt, sal_Int32 nPos)
             )
         );
 }
+}
 
 OUString ConvertMSFormatStringToSO(
         const OUString& rFormat, lang::Locale& rLocale, bool bHijri)