diff --git a/src/_cffi_src/openssl/src/osrandom_engine.c b/src/_cffi_src/openssl/src/osrandom_engine.c
index 034637c..4fcd34f 100644
--- a/src/_cffi_src/openssl/src/osrandom_engine.c
+++ b/src/_cffi_src/openssl/src/osrandom_engine.c
@@ -223,8 +223,10 @@
     int res;
 
     switch(getentropy_works) {
+#if defined(__APPLE__)
     case CRYPTOGRAPHY_OSRANDOM_GETENTROPY_FALLBACK:
         return dev_urandom_read(buffer, size);
+#endif
     case CRYPTOGRAPHY_OSRANDOM_GETENTROPY_WORKS:
         while (size > 0) {
             /* OpenBSD and macOS restrict maximum buffer size to 256. */