diff --git a/cfg/posix.cfg b/cfg/posix.cfg
index b9aa5b118..cad50db53 100644
--- a/cfg/posix.cfg
+++ b/cfg/posix.cfg
@@ -3026,14 +3026,15 @@ The function 'mktemp' is considered to be dangerous due to race conditions and s
     <arg nr="2" direction="in">
       <not-uninit/>
       <minsize type="argvalue" arg="3"/>
-      <strz/>
     </arg>
     <arg nr="3" direction="in">
       <not-uninit/>
       <not-bool/>
+      <valid>0:</valid>
     </arg>
     <arg nr="4" direction="in">
       <not-bool/>
+      <valid>0:</valid>
     </arg>
   </function>
   <!-- https://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_setattr.html -->
diff --git a/test/cfg/posix.c b/test/cfg/posix.c
index 47c1baffc..4ff1ab5f7 100644
--- a/test/cfg/posix.c
+++ b/test/cfg/posix.c
@@ -35,6 +35,13 @@
 #include <string.h>
 #include <strings.h>
 
+int invalidFunctionArgStr_mq_send(mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned msg_prio)
+{
+    const char msg = '0';
+    (void) mq_send(mqdes, &msg, 1, 0);
+    return mq_send(mqdes, msg_ptr, msg_len, 0);
+}
+
 void invalidFunctionArgStr_mbsnrtowcs(void)
 {
     wchar_t wenough[10];