diff --git a/libbuild2-autoconf/libbuild2/autoconf/checks/SIZEOF_PTHREAD_T.h b/libbuild2-autoconf/libbuild2/autoconf/checks/SIZEOF_PTHREAD_T.h
index 9ad79d1..1bedc6c 100644
--- a/libbuild2-autoconf/libbuild2/autoconf/checks/SIZEOF_PTHREAD_T.h
+++ b/libbuild2-autoconf/libbuild2/autoconf/checks/SIZEOF_PTHREAD_T.h
@@ -3,7 +3,7 @@
 #undef SIZEOF_PTHREAD_T
 
 #ifndef _WIN32
-#   ifdef defined(__APPLE__)
+#   if defined(__APPLE__)
 #       ifdef __LP64__
 #           define SIZEOF_PTHREAD_T 8
 #       else