diff --git a/dom/src/base/nsJSEnvironment.cpp b/dom/src/base/nsJSEnvironment.cpp
index 5122c5f9b7f0..5554d0644941 100644
--- a/dom/src/base/nsJSEnvironment.cpp
+++ b/dom/src/base/nsJSEnvironment.cpp
@@ -3063,7 +3063,7 @@ inline PRBool
 IsJProfAction(struct sigaction *action)
 {
     return (action->sa_sigaction &&
-            action->sa_flags == SA_RESTART | SA_SIGINFO);
+            action->sa_flags == (SA_RESTART | SA_SIGINFO));
 }
 
 void NS_JProfStartProfiling();