diff --git a/Userland/Libraries/LibC/langinfo.cpp b/Userland/Libraries/LibC/langinfo.cpp
index a44f70afe16..c59aa8f49a6 100644
--- a/Userland/Libraries/LibC/langinfo.cpp
+++ b/Userland/Libraries/LibC/langinfo.cpp
@@ -96,4 +96,10 @@ char* nl_langinfo(nl_item item)
     // so this cast is probably fine.
     return const_cast<char*>(__nl_langinfo(item));
 }
+
+char* nl_langinfo_l(nl_item item, locale_t)
+{
+    // FIXME: Support other locales.
+    return nl_langinfo(item);
+}
 }
diff --git a/Userland/Libraries/LibC/langinfo.h b/Userland/Libraries/LibC/langinfo.h
index f5836915ba6..2a8e44a34c5 100644
--- a/Userland/Libraries/LibC/langinfo.h
+++ b/Userland/Libraries/LibC/langinfo.h
@@ -8,6 +8,7 @@
 
 // Includes essentially mandated by POSIX:
 // https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/langinfo.h.html
+#include <locale.h>
 #include <nl_types.h>
 
 #include <sys/cdefs.h>
@@ -80,5 +81,6 @@ enum {
 };
 
 char* nl_langinfo(nl_item);
+char* nl_langinfo_l(nl_item, locale_t);
 
 __END_DECLS
diff --git a/Userland/Libraries/LibC/locale.cpp b/Userland/Libraries/LibC/locale.cpp
index 36ff8010d42..ff1d9a2c100 100644
--- a/Userland/Libraries/LibC/locale.cpp
+++ b/Userland/Libraries/LibC/locale.cpp
@@ -64,4 +64,21 @@ struct lconv* localeconv()
 {
     return &default_locale;
 }
+
+void freelocale(locale_t)
+{
+    // FIXME: Implement this.
+}
+
+locale_t newlocale(int, char const*, locale_t)
+{
+    // FIXME: Implement this.
+    return nullptr;
+}
+
+locale_t uselocale(locale_t loc)
+{
+    // FIXME: Implement this.
+    return loc;
+}
 }
diff --git a/Userland/Libraries/LibC/locale.h b/Userland/Libraries/LibC/locale.h
index 0fe99ba7d81..b12e77a8172 100644
--- a/Userland/Libraries/LibC/locale.h
+++ b/Userland/Libraries/LibC/locale.h
@@ -27,6 +27,14 @@ enum {
 #define LC_MESSAGES LC_MESSAGES
 };
 
+#define LC_NUMERIC_MASK (1 << LC_NUMERIC)
+#define LC_CTYPE_MASK (1 << LC_CTYPE)
+#define LC_COLLATE_MASK (1 << LC_COLLATE)
+#define LC_TIME_MASK (1 << LC_TIME)
+#define LC_MONETARY_MASK (1 << LC_MONETARY)
+#define LC_MESSAGES_MASK (1 << LC_MESSAGES)
+#define LC_ALL_MASK (LC_NUMERIC_MASK | LC_CTYPE_MASK | LC_COLLATE_MASK | LC_TIME_MASK | LC_MONETARY_MASK | LC_MESSAGES_MASK)
+
 struct lconv {
     char* decimal_point;
     char* thousands_sep;
@@ -54,7 +62,13 @@ struct lconv {
     char int_n_sign_posn;
 };
 
+struct __locale_t_impl;
+typedef struct __locale_t_impl* locale_t;
+
 struct lconv* localeconv(void);
+void freelocale(locale_t);
+locale_t newlocale(int, char const*, locale_t);
 char* setlocale(int category, char const* locale);
+locale_t uselocale(locale_t);
 
 __END_DECLS