diff --git a/cpp/ql/src/semmle/code/cpp/models/implementations/Pure.qll b/cpp/ql/src/semmle/code/cpp/models/implementations/Pure.qll
index 59b8c25700f..dd03d83848c 100644
--- a/cpp/ql/src/semmle/code/cpp/models/implementations/Pure.qll
+++ b/cpp/ql/src/semmle/code/cpp/models/implementations/Pure.qll
@@ -30,7 +30,12 @@ class PureStrFunction extends AliasFunction, ArrayFunction, TaintFunction, SideE
         name = "strtol" or
         name = "strtoll" or
         name = "strtoq" or
-        name = "strtoul"
+        name = "strtoul" or
+        name = "wcslen" or
+        name = "_mbslen" or
+        name = "_mbslen_l" or
+        name = "_mbstrlen" or
+        name = "_mbstrlen_l"
       )
     )
   }