diff --git a/src/common/datetime.cpp b/src/common/datetime.cpp
index 6db78ecd41..ba9419b5c7 100644
--- a/src/common/datetime.cpp
+++ b/src/common/datetime.cpp
@@ -935,7 +935,7 @@ void wxDateTime::GetAmPmStrings(wxString *am, wxString *pm)
     // assert, even though it is a perfectly legal use.
     if ( am )
     {
-        if (wxStrftime(buffer, sizeof buffer, _T("%p"), &tm) > 0)
+        if (wxStrftime(buffer, sizeof(buffer)/sizeof(wxChar), _T("%p"), &tm) > 0)
             *am = wxString(buffer);
         else
             *am = wxString();
@@ -943,7 +943,7 @@ void wxDateTime::GetAmPmStrings(wxString *am, wxString *pm)
     if ( pm )
     {
         tm.tm_hour = 13;
-        if (wxStrftime(buffer, sizeof buffer, _T("%p"), &tm) > 0)
+        if (wxStrftime(buffer, sizeof(buffer)/sizeof(wxChar), _T("%p"), &tm) > 0)
             *pm = wxString(buffer);
         else
             *pm = wxString();