diff --git a/src/unix/fs.c b/src/unix/fs.c
index 596e69da7..f4b4280ca 100644
--- a/src/unix/fs.c
+++ b/src/unix/fs.c
@@ -47,7 +47,7 @@
 
 #if defined(__DragonFly__)        ||                                      \
     defined(__FreeBSD__)          ||                                      \
-    defined(__FreeBSD_kernel_)    ||                                      \
+    defined(__FreeBSD_kernel__)   ||                                      \
     defined(__OpenBSD__)          ||                                      \
     defined(__NetBSD__)
 # define HAVE_PREADV 1