diff --git a/kdesu/process.cpp b/kdesu/process.cpp
index edd80c67d..b977a1342 100644
--- a/kdesu/process.cpp
+++ b/kdesu/process.cpp
@@ -359,6 +359,7 @@ int PtyProcess::exec(const TQCString &command, const QCStringList &args)
         putenv(const_cast<TQCString&>(*it).data());
     }
     unsetenv("TDE_FULL_SESSION");
+    unsetenv("XDG_RUNTIME_DIR");
     
     // set temporarily LC_ALL to C, for su (to be able to parse "Password:")
     const char* old_lc_all = getenv( "LC_ALL" );