diff --git a/cfg/posix.cfg b/cfg/posix.cfg
index ed9c02fd5..39bfad693 100644
--- a/cfg/posix.cfg
+++ b/cfg/posix.cfg
@@ -3552,9 +3552,10 @@ The function 'mktemp' is considered to be dangerous due to race conditions and s
     <returnValue type="size_t"/>
     <use-retval/>
     <noreturn>false</noreturn>
-    <arg nr="1" direction="out">
-      <not-null/>
-    </arg>
+    <!-- If dest is NULL, len is ignored, and the conversion proceeds as
+       above, except that the converted wide characters are not written
+       out to memory, and that no length limit exists. -->
+    <arg nr="1" direction="out"/>
     <arg nr="2" direction="in">
       <not-uninit/>
       <not-null/>
@@ -3570,9 +3571,9 @@ The function 'mktemp' is considered to be dangerous due to race conditions and s
       <not-bool/>
       <valid>0:</valid>
     </arg>
-    <arg nr="5" direction="in">
-      <not-null/>
-    </arg>
+    <!-- In both of the above cases, if ps is NULL, a static anonymous
+       state known only to the mbsrtowcs() function is used instead. -->
+    <arg nr="5" direction="in"/>
   </function>
   <!-- https://pubs.opengroup.org/onlinepubs/9699919799/functions/regcomp.html -->
   <!-- int regcomp(regex_t *restrict preg, const char *restrict pattern, int cflags); -->