diff --git a/libc/include/bits/wctype.h b/libc/include/bits/wctype.h
index b98e500..c968d71 100644
--- a/libc/include/bits/wctype.h
+++ b/libc/include/bits/wctype.h
@@ -58,8 +58,8 @@
 int iswctype(wint_t, wctype_t);
 
 typedef const void* wctrans_t;
-wint_t towctrans(wint_t, wctrans_t) __INTRODUCED_IN_FUTURE;
-wctrans_t wctrans(const char*) __INTRODUCED_IN_FUTURE;
+wint_t towctrans(wint_t, wctrans_t) __INTRODUCED_IN_FUTURE __VERSIONER_NO_GUARD;
+wctrans_t wctrans(const char*) __INTRODUCED_IN_FUTURE __VERSIONER_NO_GUARD;
 
 __END_DECLS
 
diff --git a/libc/include/locale.h b/libc/include/locale.h
index a681a17..c1b6299 100644
--- a/libc/include/locale.h
+++ b/libc/include/locale.h
@@ -96,7 +96,7 @@
   char int_n_sign_posn;
 };
 
-struct lconv* localeconv(void) __INTRODUCED_IN(21);
+struct lconv* localeconv(void) __INTRODUCED_IN(21) __VERSIONER_NO_GUARD;
 
 locale_t duplocale(locale_t) __INTRODUCED_IN(21);
 void freelocale(locale_t) __INTRODUCED_IN(21);
diff --git a/libc/include/math.h b/libc/include/math.h
index 37aa2cc..3b12764 100644
--- a/libc/include/math.h
+++ b/libc/include/math.h
@@ -259,11 +259,12 @@
 long double fabsl(long double) __pure2;
 long double fdiml(long double, long double);
 long double floorl(long double);
-long double fmal(long double, long double, long double) __INTRODUCED_IN(21);
+long double fmal(long double, long double, long double) __INTRODUCED_IN(21) __VERSIONER_NO_GUARD;
 long double fmaxl(long double, long double) __pure2;
 long double fminl(long double, long double) __pure2;
 long double fmodl(long double, long double) __INTRODUCED_IN(21);
-long double frexpl(long double value, int*) __INTRODUCED_IN(21); /* fundamentally !__pure2 */
+long double frexpl(long double value, int*)
+    __INTRODUCED_IN(21) __VERSIONER_NO_GUARD; /* fundamentally !__pure2 */
 long double hypotl(long double, long double) __INTRODUCED_IN(21);
 int ilogbl(long double) __pure2;
 long double ldexpl(long double, int);
@@ -280,10 +281,10 @@
 long double modfl(long double, long double*) __INTRODUCED_IN(21); /* fundamentally !__pure2 */
 long double nanl(const char*) __pure2 __INTRODUCED_IN(13);
 long double nearbyintl(long double) __INTRODUCED_IN(21);
-long double nextafterl(long double, long double) __INTRODUCED_IN(21);
-double nexttoward(double, long double) __INTRODUCED_IN(18);
+long double nextafterl(long double, long double) __INTRODUCED_IN(21) __VERSIONER_NO_GUARD;
+double nexttoward(double, long double) __INTRODUCED_IN(18) __VERSIONER_NO_GUARD;
 float nexttowardf(float, long double);
-long double nexttowardl(long double, long double) __INTRODUCED_IN(18);
+long double nexttowardl(long double, long double) __INTRODUCED_IN(18) __VERSIONER_NO_GUARD;
 long double powl(long double, long double) __INTRODUCED_IN(21);
 long double remainderl(long double, long double) __INTRODUCED_IN(21);
 long double remquol(long double, long double, int*) __INTRODUCED_IN(21);
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index 28cd4a8..6b0ec12 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -147,14 +147,23 @@
 const char* getprogname(void) __INTRODUCED_IN(21);
 void setprogname(const char*) __INTRODUCED_IN(21);
 
-int mblen(const char*, size_t) __INTRODUCED_IN_FUTURE;
+int mblen(const char*, size_t) __INTRODUCED_IN_FUTURE __VERSIONER_NO_GUARD;
 size_t mbstowcs(wchar_t*, const char*, size_t);
-int mbtowc(wchar_t*, const char*, size_t) __INTRODUCED_IN(21);
-int wctomb(char*, wchar_t) __INTRODUCED_IN(21);
+int mbtowc(wchar_t*, const char*, size_t) __INTRODUCED_IN(21) __VERSIONER_NO_GUARD;
+int wctomb(char*, wchar_t) __INTRODUCED_IN(21) __VERSIONER_NO_GUARD;
+
 size_t wcstombs(char*, const wchar_t*, size_t);
 
+#if __ANDROID_API__ >= 21
 size_t __ctype_get_mb_cur_max(void) __INTRODUCED_IN(21);
 #define MB_CUR_MAX __ctype_get_mb_cur_max()
+#else
+/*
+ * 4 is only true for UTF-8 locales, but that's what we default to. We'll need
+ * the NDK compatibility library to fix this properly.
+ */
+#define MB_CUR_MAX 4
+#endif
 
 #if defined(__BIONIC_FORTIFY)