diff --git a/reference/filesystem/functions/basename.xml b/reference/filesystem/functions/basename.xml
index 0396d4e896..6ed4f3966a 100644
--- a/reference/filesystem/functions/basename.xml
+++ b/reference/filesystem/functions/basename.xml
@@ -29,6 +29,8 @@
basename is locale aware, so for it to see the
correct basename with multibyte character paths, the matching locale must
be set using the setlocale function.
+ If path contains characters which are invalid for the
+ current locale, the behavior of basename is undefined.
diff --git a/reference/filesystem/functions/dirname.xml b/reference/filesystem/functions/dirname.xml
index d9bcfe001b..a059fce237 100644
--- a/reference/filesystem/functions/dirname.xml
+++ b/reference/filesystem/functions/dirname.xml
@@ -27,9 +27,16 @@
- dirname is locale aware, so for it to see the
- correct directory name with multibyte character paths, the matching locale must
- be set using the setlocale function.
+ On Windows, dirname assumes the currently set codepage, so for it to see the
+ correct directory name with multibyte character paths, the matching codepage must
+ be set.
+ If path contains characters which are invalid for the
+ current codepage, the behavior of basename is undefined.
+
+
+ On other systems, dirname assumes path
+ to be encoded in an ASCII compatible encoding. Otherwise the behavior of the
+ the function is undefined.