diff --git a/libc/include/math.h b/libc/include/math.h
index 343ab98..59161bf 100644
--- a/libc/include/math.h
+++ b/libc/include/math.h
@@ -350,7 +350,11 @@
 double gamma_r(double __x, int* _Nonnull __sign);
 double lgamma_r(double __x, int* _Nonnull __sign);
 double significand(double __x);
+
+#if __BIONIC_AVAILABILITY_GUARD(23)
 long double lgammal_r(long double __x, int* _Nonnull __sign) __INTRODUCED_IN(23);
+#endif /* __BIONIC_AVAILABILITY_GUARD(23) */
+
 long double significandl(long double __x);
 float dremf(float __x, float __y);
 int finitef(float __x) __attribute_const__;