diff --git a/dlls/mlang/mlang.c b/dlls/mlang/mlang.c
index 2f73f1f..87aa8b5 100644
--- a/dlls/mlang/mlang.c
+++ b/dlls/mlang/mlang.c
@@ -629,6 +629,7 @@ HRESULT WINAPI ConvertINetString(
 
         TRACE("convert %s from %d to %d\n", debugstr_a(pSrcStr), dwSrcEncoding, dwDstEncoding);
 
+        cDstSizeW = 0;
         hr = ConvertINetMultiByteToUnicode(pdwMode, dwSrcEncoding, pSrcStr, pcSrcSize, NULL, &cDstSizeW);
         if (hr != S_OK)
             return hr;
-- 
1.5.4.3