diff --git a/libc/include/bits/fortify/unistd.h b/libc/include/bits/fortify/unistd.h
index 543c3c7..547a168 100644
--- a/libc/include/bits/fortify/unistd.h
+++ b/libc/include/bits/fortify/unistd.h
@@ -67,7 +67,8 @@
                      "in call to '" #fn "', '" #what "' bytes overflows the given object")
 
 #define __bos_trivially_not_lt_no_overflow(bos_val, index)  \
-      __bos_dynamic_check_impl_and((bos_val), >=, (index), (bos_val) <= SSIZE_MAX)
+      ((__bos_dynamic_check_impl_and((bos_val), >=, (index), (bos_val) <= SSIZE_MAX) && \
+        __builtin_constant_p(index) && (index) <= SSIZE_MAX))
 
 #if __ANDROID_API__ >= __ANDROID_API_N__
 __BIONIC_FORTIFY_INLINE