diff --git a/src/unix/mimetype.cpp b/src/unix/mimetype.cpp
index de87222041..8c5508c557 100644
--- a/src/unix/mimetype.cpp
+++ b/src/unix/mimetype.cpp
@@ -2503,7 +2503,8 @@ bool wxMimeTypesManagerImpl::ReadMailcap(const wxString& strFileName,
 
         if ( data.needsterminal )
         {
-            data.cmdOpen.Printf(_T("xterm -e sh -c '%s'"), data.cmdOpen.c_str());
+            data.cmdOpen = wxString::Format(_T("xterm -e sh -c '%s'"),
+                                            data.cmdOpen.c_str());
         }
 
         if ( !data.cmdOpen.empty() )