diff --git a/dlls/ntdll/ntdll.spec b/dlls/ntdll/ntdll.spec
index 95581ec6fad..097140fc756 100644
--- a/dlls/ntdll/ntdll.spec
+++ b/dlls/ntdll/ntdll.spec
@@ -1431,6 +1431,7 @@
 @ cdecl -private strncat(str str long) NTDLL_strncat
 @ cdecl -private strncmp(str str long) NTDLL_strncmp
 @ cdecl -private strncpy(ptr str long) NTDLL_strncpy
+@ cdecl -private strnlen(ptr long) NTDLL_strnlen
 @ cdecl -private strpbrk(str str) NTDLL_strpbrk
 @ cdecl -private strrchr(str long) NTDLL_strrchr
 @ cdecl -private strspn(str str) NTDLL_strspn
diff --git a/dlls/ntdll/string.c b/dlls/ntdll/string.c
index c349add5436..e0bf5be1640 100644
--- a/dlls/ntdll/string.c
+++ b/dlls/ntdll/string.c
@@ -163,6 +163,15 @@ char * __cdecl NTDLL_strncpy( char *dst, const char *src, size_t len )
 }
 
 
+/*********************************************************************
+ *                  strnlen   (NTDLL.@)
+ */
+size_t __cdecl NTDLL_strnlen( const char *str, size_t len )
+{
+    return strnlen( str, len );
+}
+
+
 /*********************************************************************
  *                  strpbrk   (NTDLL.@)
  */