diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index 7dde6b4..8e74716 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -30,6 +30,7 @@
 #include <compositionengine/Output.h>
 #include <compositionengine/OutputLayer.h>
 #include <compositionengine/impl/OutputLayerCompositionState.h>
+#include <ftl/concat.h>
 #include <log/log.h>
 #include <ui/DebugUtils.h>
 #include <ui/GraphicBuffer.h>
@@ -148,16 +149,17 @@
     return mUpdateDeviceProductInfoOnHotplugReconnect;
 }
 
-bool HWComposer::onVsync(hal::HWDisplayId hwcDisplayId, nsecs_t timestamp) {
-    const auto displayId = toPhysicalDisplayId(hwcDisplayId);
-    if (!displayId) {
+std::optional<PhysicalDisplayId> HWComposer::onVsync(hal::HWDisplayId hwcDisplayId,
+                                                     nsecs_t timestamp) {
+    const auto displayIdOpt = toPhysicalDisplayId(hwcDisplayId);
+    if (!displayIdOpt) {
         LOG_HWC_DISPLAY_ERROR(hwcDisplayId, "Invalid HWC display");
-        return false;
+        return {};
     }
 
-    RETURN_IF_INVALID_DISPLAY(*displayId, false);
+    RETURN_IF_INVALID_DISPLAY(*displayIdOpt, {});
 
-    auto& displayData = mDisplayData[*displayId];
+    auto& displayData = mDisplayData[*displayIdOpt];
 
     {
         // There have been reports of HWCs that signal several vsync events
@@ -166,18 +168,18 @@
         // out here so they don't cause havoc downstream.
         if (timestamp == displayData.lastPresentTimestamp) {
             ALOGW("Ignoring duplicate VSYNC event from HWC for display %s (t=%" PRId64 ")",
-                  to_string(*displayId).c_str(), timestamp);
-            return false;
+                  to_string(*displayIdOpt).c_str(), timestamp);
+            return {};
         }
 
         displayData.lastPresentTimestamp = timestamp;
     }
 
-    const auto tag = "HW_VSYNC_" + to_string(*displayId);
+    const ftl::Concat tag("HW_VSYNC_", displayIdOpt->value);
     ATRACE_INT(tag.c_str(), displayData.vsyncTraceToggle);
     displayData.vsyncTraceToggle = !displayData.vsyncTraceToggle;
 
-    return true;
+    return displayIdOpt;
 }
 
 size_t HWComposer::getMaxVirtualDisplayCount() const {
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index f6155d2..acebfb2 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -221,7 +221,10 @@
     // TODO(b/157555476): Remove when the framework has proper support for headless mode
     virtual bool updatesDeviceProductInfoOnHotplugReconnect() const = 0;
 
-    virtual bool onVsync(hal::HWDisplayId, nsecs_t timestamp) = 0;
+    // Called when a vsync happens. If the vsync is valid, returns the
+    // corresponding PhysicalDisplayId. Otherwise returns nullopt.
+    virtual std::optional<PhysicalDisplayId> onVsync(hal::HWDisplayId, nsecs_t timestamp) = 0;
+
     virtual void setVsyncEnabled(PhysicalDisplayId, hal::Vsync enabled) = 0;
 
     virtual bool isConnected(PhysicalDisplayId) const = 0;
@@ -402,7 +405,7 @@
 
     bool updatesDeviceProductInfoOnHotplugReconnect() const override;
 
-    bool onVsync(hal::HWDisplayId, nsecs_t timestamp) override;
+    std::optional<PhysicalDisplayId> onVsync(hal::HWDisplayId, nsecs_t timestamp) override;
     void setVsyncEnabled(PhysicalDisplayId, hal::Vsync enabled) override;
 
     bool isConnected(PhysicalDisplayId) const override;