suppress warnings by parenthesizing unclear expressions

1 files changed, 1 insertions, 1 deletions

diff --git a/thread.c b/thread.c
index 86676d7bc6..336ac7836c 100644
--- a/thread.c
+++ b/thread.c
@@ -1670,7 +1670,7 @@ rb_nogvl(void *(*func)(void *), void *data1,
     int saved_errno = 0;
     VALUE ubf_th = Qfalse;
 
-    if (ubf == RUBY_UBF_IO || ubf == RUBY_UBF_PROCESS) {
+    if ((ubf == RUBY_UBF_IO) || (ubf == RUBY_UBF_PROCESS)) {
 	ubf = ubf_select;
 	data2 = th;
     }