diff --git a/json_tokener.c b/json_tokener.c
index 516142a..c1ca2cd 100644
--- a/json_tokener.c
+++ b/json_tokener.c
@@ -314,6 +314,15 @@ struct json_object *json_tokener_parse_verbose(const char *str, enum json_tokene
 
 /* End optimization macro defs */
 
+#ifdef HAVE_USELOCALE
+/* One-time C-numeric locale, created on first call and reused forever.
+ * Avoids per-call duplocale() overhead and the memory leak seen on AIX
+ * where freelocale() does not release all locale category memory.
+ * Freed on library unload by json_tokener_locale_fini().
+ */
+static locale_t c_numeric_locale = (locale_t)0;
+#endif /* HAVE_USELOCALE */
+
 struct json_object *json_tokener_parse_ex(struct json_tokener *tok, const char *str, int len)
 {
 	struct json_object *obj = NULL;
@@ -323,7 +332,6 @@ struct json_object *json_tokener_parse_ex(struct json_tokener *tok, const char *
 
 #ifdef HAVE_USELOCALE
 	locale_t oldlocale = uselocale(NULL);
-	locale_t newloc;
 #elif defined(HAVE_SETLOCALE)
 	char *oldlocale = NULL;
 #endif
@@ -345,33 +353,16 @@ struct json_object *json_tokener_parse_ex(struct json_tokener *tok, const char *
 
 #ifdef HAVE_USELOCALE
 	{
-#ifdef HAVE_DUPLOCALE
-		locale_t duploc = duplocale(oldlocale);
-		if (duploc == NULL && errno == ENOMEM)
+		if (c_numeric_locale == (locale_t)0)
 		{
-			tok->err = json_tokener_error_memory;
-			return NULL;
+			c_numeric_locale = newlocale(LC_NUMERIC_MASK, "C", (locale_t)0);
+			if (c_numeric_locale == (locale_t)0)
+			{
+				tok->err = json_tokener_error_memory;
+				return NULL;
+			}
 		}
-		newloc = newlocale(LC_NUMERIC_MASK, "C", duploc);
-#else
-		newloc = newlocale(LC_NUMERIC_MASK, "C", oldlocale);
-#endif
-		if (newloc == NULL)
-		{
-			tok->err = json_tokener_error_memory;
-#ifdef HAVE_DUPLOCALE
-			freelocale(duploc);
-#endif
-			return NULL;
-		}
-#ifdef NEWLOCALE_NEEDS_FREELOCALE
-#ifdef HAVE_DUPLOCALE
-		// Older versions of FreeBSD (<12.4) don't free the locale
-		// passed to newlocale(), so do it here
-		freelocale(duploc);
-#endif
-#endif
-		uselocale(newloc);
+		uselocale(c_numeric_locale);
 	}
 #elif defined(HAVE_SETLOCALE)
 	{
@@ -1409,7 +1400,6 @@ out:
 
 #ifdef HAVE_USELOCALE
 	uselocale(oldlocale);
-	freelocale(newloc);
 #elif defined(HAVE_SETLOCALE)
 	setlocale(LC_NUMERIC, oldlocale);
 	free(oldlocale);
@@ -1476,3 +1466,20 @@ static int json_tokener_parse_double(const char *buf, int len, double *retval)
 		return 0; // It worked
 	return 1;
 }
+
+#ifdef HAVE_USELOCALE
+/* Release the static C-numeric locale when the library is unloaded.
+ * This keeps Valgrind clean.
+ */
+#if defined(__GNUC__) || defined(__clang__)
+__attribute__((destructor))
+static void json_tokener_locale_fini(void)
+{
+	if (c_numeric_locale != (locale_t)0)
+	{
+		freelocale(c_numeric_locale);
+		c_numeric_locale = (locale_t)0;
+	}
+}
+#endif /* __GNUC__ || __clang__ */
+#endif /* HAVE_USELOCALE */