diff --git a/services/core/java/com/android/server/am/CachedAppOptimizer.java b/services/core/java/com/android/server/am/CachedAppOptimizer.java
index 86ca6994eeed9..b18d390476f02 100644
--- a/services/core/java/com/android/server/am/CachedAppOptimizer.java
+++ b/services/core/java/com/android/server/am/CachedAppOptimizer.java
@@ -1056,7 +1056,9 @@ public final class CachedAppOptimizer {
         if(wakefulness == PowerManagerInternal.WAKEFULNESS_AWAKE) {
             // Remove any pending compaction we may have scheduled to happen while screen was off
             Slog.e(TAG_AM, "Cancel pending or running compactions as system is awake");
-            mPendingCompactionProcesses.clear();
+            synchronized(mProcLock) {
+                mPendingCompactionProcesses.clear();
+            }
             cancelCompaction();
         }
     }