diff --git a/libc/include/locale.h b/libc/include/locale.h
index b6dbfdb..4efc564 100644
--- a/libc/include/locale.h
+++ b/libc/include/locale.h
@@ -51,12 +51,41 @@
 
 extern char* setlocale(int, const char*);
 
-#if !defined(__LP64__)
-// TODO: LP32 had these bogus declarations but LP64 should have a real struct lconv and localeconv(3).
+#if defined(__LP64__)
+struct lconv {
+    char* decimal_point;
+    char* thousands_sep;
+    char* grouping;
+    char* int_curr_symbol;
+    char* currency_symbol;
+    char* mon_decimal_point;
+    char* mon_thousands_sep;
+    char* mon_grouping;
+    char* positive_sign;
+    char* negative_sign;
+    char  int_frac_digits;
+    char  frac_digits;
+    char  p_cs_precedes;
+    char  p_sep_by_space;
+    char  n_cs_precedes;
+    char  n_sep_by_space;
+    char  p_sign_posn;
+    char  n_sign_posn;
+    /* ISO-C99 */
+    char  int_p_cs_precedes;
+    char  int_p_sep_by_space;
+    char  int_n_cs_precedes;
+    char  int_n_sep_by_space;
+    char  int_p_sign_posn;
+    char  int_n_sign_posn;
+};
+#else
+// Keep old declaration for ILP32 for compatibility
 struct lconv { };
-struct lconv* localeconv(void);
 #endif
 
+struct lconv* localeconv(void);
+
 __END_DECLS
 
 #endif /* _LOCALE_H_ */
diff --git a/libc/include/sys/localedef.h b/libc/include/sys/localedef.h
new file mode 100644
index 0000000..b6b5eb1
--- /dev/null
+++ b/libc/include/sys/localedef.h
@@ -0,0 +1,101 @@
+/*	$OpenBSD: localedef.h,v 1.3 1996/04/21 22:31:47 deraadt Exp $	*/
+/*	$NetBSD: localedef.h,v 1.4 1996/04/09 20:55:31 cgd Exp $	*/
+
+/*
+ * Copyright (c) 1994 Winning Strategies, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *      This product includes software developed by Winning Strategies, Inc.
+ * 4. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _SYS_LOCALEDEF_H_
+#define _SYS_LOCALEDEF_H_
+
+#include <sys/param.h>
+#include <sys/types.h>
+
+typedef struct
+{
+	char *yesexpr;
+	char *noexpr;
+	char *yesstr;
+	char *nostr;
+} _MessagesLocale;
+
+extern const _MessagesLocale *_CurrentMessagesLocale;
+extern const _MessagesLocale  _DefaultMessagesLocale;
+
+
+typedef struct
+{
+	char *int_curr_symbol;
+	char *currency_symbol;
+	char *mon_decimal_point;
+	char *mon_thousands_sep;
+	char *mon_grouping;
+	char *positive_sign;
+	char *negative_sign;
+	char int_frac_digits;
+	char frac_digits;
+	char p_cs_precedes;
+	char p_sep_by_space;
+	char n_cs_precedes;
+	char n_sep_by_space;
+	char p_sign_posn;
+	char n_sign_posn;
+} _MonetaryLocale;
+
+extern const _MonetaryLocale *_CurrentMonetaryLocale;
+extern const _MonetaryLocale  _DefaultMonetaryLocale;
+
+
+typedef struct
+{
+	const char *decimal_point;
+	const char *thousands_sep;
+	const char *grouping;
+} _NumericLocale;
+
+extern const _NumericLocale *_CurrentNumericLocale;
+extern const _NumericLocale  _DefaultNumericLocale;
+
+
+typedef struct {
+	const char *abday[7];
+	const char *day[7];
+	const char *abmon[12];
+	const char *mon[12];
+	const char *am_pm[2];
+	const char *d_t_fmt;
+	const char *d_fmt;
+	const char *t_fmt;
+	const char *t_fmt_ampm;
+} _TimeLocale;
+
+extern const _TimeLocale *_CurrentTimeLocale;
+extern const _TimeLocale  _DefaultTimeLocale;
+
+#endif /* !_SYS_LOCALEDEF_H_ */