diff --git a/Userland/Libraries/LibC/wchar.cpp b/Userland/Libraries/LibC/wchar.cpp
index 487ad0b29ac..726d998bc96 100644
--- a/Userland/Libraries/LibC/wchar.cpp
+++ b/Userland/Libraries/LibC/wchar.cpp
@@ -159,4 +159,40 @@ wint_t btowc(int)
     dbgln("FIXME: Implement btowc()");
     TODO();
 }
+
+size_t mbrtowc(wchar_t*, const char*, size_t, mbstate_t*)
+{
+    dbgln("FIXME: Implement mbrtowc()");
+    TODO();
+}
+
+size_t mbrlen(const char*, size_t, mbstate_t*)
+{
+    dbgln("FIXME: Implement mbrlen()");
+    TODO();
+}
+
+size_t wcrtomb(char*, wchar_t, mbstate_t*)
+{
+    dbgln("FIXME: Implement wcrtomb()");
+    TODO();
+}
+
+int wcscoll(const wchar_t*, const wchar_t*)
+{
+    dbgln("FIXME: Implement wcscoll()");
+    TODO();
+}
+
+int wctob(wint_t)
+{
+    dbgln("FIXME: Implement wctob()");
+    TODO();
+}
+
+int mbsinit(const mbstate_t*)
+{
+    dbgln("FIXME: Implement mbsinit()");
+    TODO();
+}
 }
diff --git a/Userland/Libraries/LibC/wchar.h b/Userland/Libraries/LibC/wchar.h
index ef7b447531d..a707bbf23f0 100644
--- a/Userland/Libraries/LibC/wchar.h
+++ b/Userland/Libraries/LibC/wchar.h
@@ -34,5 +34,11 @@ wchar_t* wcstok(wchar_t*, const wchar_t*, wchar_t**);
 long wcstol(const wchar_t*, wchar_t**, int);
 long long wcstoll(const wchar_t*, wchar_t**, int);
 wint_t btowc(int c);
+size_t mbrtowc(wchar_t*, const char*, size_t, mbstate_t*);
+size_t mbrlen(const char*, size_t, mbstate_t*);
+size_t wcrtomb(char*, wchar_t, mbstate_t*);
+int wcscoll(const wchar_t*, const wchar_t*);
+int wctob(wint_t);
+int mbsinit(const mbstate_t*);
 
 __END_DECLS