Index: uspace/lib/c/include/string.h
===================================================================
--- uspace/lib/c/include/string.h	(revision 0f6a85ae5bc94c0e622f65a41fbc8e9b809c7667)
+++ uspace/lib/c/include/string.h	(revision 098e16a542a995bd6a49397ae5c774a6dc91a3d1)
@@ -64,5 +64,5 @@
 extern size_t strlen(const char *);
 
-#if defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) || defined(_LIBC_SOURCE)
+#if defined(_HELENOS_SOURCE) || defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) || defined(_LIBC_SOURCE)
 extern size_t strnlen(const char *, size_t);
 extern char *strdup(const char *);