diff --git a/packages/react-reconciler/src/ReactFiberScheduler.js b/packages/react-reconciler/src/ReactFiberScheduler.js
index a7e60f17b1e66..273b339e9a41a 100644
--- a/packages/react-reconciler/src/ReactFiberScheduler.js
+++ b/packages/react-reconciler/src/ReactFiberScheduler.js
@@ -1841,6 +1841,11 @@ function findHighestPriorityRoot() {
         if (root === lastScheduledRoot) {
           break;
         }
+        if (highestPriorityWork === Sync) {
+          // Sync is highest priority by definition so
+          // we can stop searching.
+          break;
+        }
         previousScheduledRoot = root;
         root = root.nextScheduledRoot;
       }