diff --git a/libc/include/android/legacy_signal_inlines.h b/libc/include/android/legacy_signal_inlines.h
index 90eda7d..a673446 100644
--- a/libc/include/android/legacy_signal_inlines.h
+++ b/libc/include/android/legacy_signal_inlines.h
@@ -45,12 +45,16 @@
 int __libc_current_sigrtmin() __attribute__((__weak__)) __VERSIONER_NO_GUARD;
 
 static __inline int __ndk_legacy___libc_current_sigrtmax() {
-  if (__libc_current_sigrtmax) return __libc_current_sigrtmax();
+  if (__builtin_available(android 21, *)) {
+    return __libc_current_sigrtmax();
+  }
   return __SIGRTMAX; /* Should match __libc_current_sigrtmax. */
 }
 
 static __inline int __ndk_legacy___libc_current_sigrtmin() {
-  if (__libc_current_sigrtmin) return __libc_current_sigrtmin();
+  if (__builtin_available(android 21, *)) {
+    return __libc_current_sigrtmin();
+  }
   return __SIGRTMIN + 7; /* Should match __libc_current_sigrtmin. */
 }