diff --git a/cfg/posix.cfg b/cfg/posix.cfg
index bccaece39..5f64d8a5a 100644
--- a/cfg/posix.cfg
+++ b/cfg/posix.cfg
@@ -244,6 +244,7 @@
   </function>
   <function name="strcasecmp">
     <noreturn>false</noreturn>
+    <pure/>
     <leak-ignore/>
     <arg nr="1">
       <not-uninit/>
@@ -256,6 +257,7 @@
   </function>
   <function name="strncasecmp">
     <noreturn>false</noreturn>
+    <pure/>
     <leak-ignore/>
     <arg nr="1">
       <not-uninit/>
diff --git a/cfg/std.cfg b/cfg/std.cfg
index d47eb8aec..525173a10 100644
--- a/cfg/std.cfg
+++ b/cfg/std.cfg
@@ -3140,6 +3140,7 @@
   <function name="strncmp">
     <use-retval/>
     <noreturn>false</noreturn>
+    <pure/>
     <leak-ignore/>
     <arg nr="1">
       <not-null/>
@@ -3157,6 +3158,7 @@
   <function name="wcsncmp">
     <use-retval/>
     <noreturn>false</noreturn>
+    <pure/>
     <leak-ignore/>
     <arg nr="1">
       <not-null/>