diff --git a/cfg/windows.cfg b/cfg/windows.cfg
index 90f4cf3ca..66601f3cb 100644
--- a/cfg/windows.cfg
+++ b/cfg/windows.cfg
@@ -3320,4 +3320,35 @@ HFONT CreateFont(
       <not-uninit/>
     </arg>
   </function>
+  <!-- size_t _mbslen_l( const unsigned char *str, _locale_t locale);  -->
+  <!-- size_t _mbstrlen_l( const char *str, _locale_t locale ); -->
+  <function name="_mbslen_l,_mbstrlen_l">
+    <use-retval/>
+    <pure/>
+    <noreturn>false</noreturn>
+    <leak-ignore/>
+    <returnValue>strlen(arg1)</returnValue>
+    <arg nr="1">
+      <not-null/>
+      <not-uninit/>
+      <strz/>
+    </arg>
+    <arg nr="2">
+      <not-uninit/>
+    </arg>
+  </function>
+  <!-- size_t _mbslen( const unsigned char *str );  -->
+  <!-- size_t _mbstrlen( const char *str ); -->
+  <function name="_mbslen,_mbstrlen,_tcslen,_tcsclen">
+    <use-retval/>
+    <pure/>
+    <noreturn>false</noreturn>
+    <leak-ignore/>
+    <returnValue>strlen(arg1)</returnValue>
+    <arg nr="1">
+      <not-null/>
+      <not-uninit/>
+      <strz/>
+    </arg>
+  </function>
 </def>