diff --git a/graphics/composer/2.1/utils/vts/GraphicsComposerCallback.cpp b/graphics/composer/2.1/utils/vts/GraphicsComposerCallback.cpp
index 1ead138..ccbc5b1 100644
--- a/graphics/composer/2.1/utils/vts/GraphicsComposerCallback.cpp
+++ b/graphics/composer/2.1/utils/vts/GraphicsComposerCallback.cpp
@@ -30,7 +30,7 @@
 
 std::vector<Display> GraphicsComposerCallback::getDisplays() const {
     std::lock_guard<std::mutex> lock(mMutex);
-    return std::vector<Display>(mDisplays.begin(), mDisplays.end());
+    return mDisplays;
 }
 
 int GraphicsComposerCallback::getInvalidHotplugCount() const {
@@ -51,12 +51,17 @@
 Return<void> GraphicsComposerCallback::onHotplug(Display display, Connection connection) {
     std::lock_guard<std::mutex> lock(mMutex);
 
+    auto it = std::find(mDisplays.begin(), mDisplays.end(), display);
     if (connection == Connection::CONNECTED) {
-        if (!mDisplays.insert(display).second) {
+        if (it == mDisplays.end()) {
+            mDisplays.push_back(display);
+        } else {
             mInvalidHotplugCount++;
         }
     } else if (connection == Connection::DISCONNECTED) {
-        if (!mDisplays.erase(display)) {
+        if (it != mDisplays.end()) {
+            mDisplays.erase(it);
+        } else {
             mInvalidHotplugCount++;
         }
     }
@@ -67,7 +72,8 @@
 Return<void> GraphicsComposerCallback::onRefresh(Display display) {
     std::lock_guard<std::mutex> lock(mMutex);
 
-    if (mDisplays.count(display) == 0) {
+    auto it = std::find(mDisplays.begin(), mDisplays.end(), display);
+    if (it == mDisplays.end()) {
         mInvalidRefreshCount++;
     }
 
@@ -77,7 +83,8 @@
 Return<void> GraphicsComposerCallback::onVsync(Display display, int64_t) {
     std::lock_guard<std::mutex> lock(mMutex);
 
-    if (!mVsyncAllowed || mDisplays.count(display) == 0) {
+    auto it = std::find(mDisplays.begin(), mDisplays.end(), display);
+    if (!mVsyncAllowed || it == mDisplays.end()) {
         mInvalidVsyncCount++;
     }
 
diff --git a/graphics/composer/2.1/utils/vts/include/composer-vts/2.1/GraphicsComposerCallback.h b/graphics/composer/2.1/utils/vts/include/composer-vts/2.1/GraphicsComposerCallback.h
index e3c348f..da64052 100644
--- a/graphics/composer/2.1/utils/vts/include/composer-vts/2.1/GraphicsComposerCallback.h
+++ b/graphics/composer/2.1/utils/vts/include/composer-vts/2.1/GraphicsComposerCallback.h
@@ -19,7 +19,7 @@
 #include <android/hardware/graphics/composer/2.1/IComposerCallback.h>
 
 #include <mutex>
-#include <unordered_set>
+#include <vector>
 
 namespace android {
 namespace hardware {
@@ -48,7 +48,7 @@
 
     mutable std::mutex mMutex;
     // the set of all currently connected displays
-    std::unordered_set<Display> mDisplays;
+    std::vector<Display> mDisplays;
     // true only when vsync is enabled
     bool mVsyncAllowed = true;
 
diff --git a/graphics/composer/2.4/utils/vts/GraphicsComposerCallback.cpp b/graphics/composer/2.4/utils/vts/GraphicsComposerCallback.cpp
index c9366a8..51e1ab7 100644
--- a/graphics/composer/2.4/utils/vts/GraphicsComposerCallback.cpp
+++ b/graphics/composer/2.4/utils/vts/GraphicsComposerCallback.cpp
@@ -25,7 +25,7 @@
 
 std::vector<Display> GraphicsComposerCallback::getDisplays() const {
     std::lock_guard<std::mutex> lock(mMutex);
-    return std::vector<Display>(mDisplays.begin(), mDisplays.end());
+    return mDisplays;
 }
 
 int32_t GraphicsComposerCallback::getInvalidHotplugCount() const {
@@ -71,12 +71,17 @@
 Return<void> GraphicsComposerCallback::onHotplug(Display display, Connection connection) {
     std::lock_guard<std::mutex> lock(mMutex);
 
+    auto it = std::find(mDisplays.begin(), mDisplays.end(), display);
     if (connection == Connection::CONNECTED) {
-        if (!mDisplays.insert(display).second) {
+        if (it == mDisplays.end()) {
+            mDisplays.push_back(display);
+        } else {
             mInvalidHotplugCount++;
         }
     } else if (connection == Connection::DISCONNECTED) {
-        if (!mDisplays.erase(display)) {
+        if (it != mDisplays.end()) {
+            mDisplays.erase(it);
+        } else {
             mInvalidHotplugCount++;
         }
     }
@@ -87,7 +92,8 @@
 Return<void> GraphicsComposerCallback::onRefresh(Display display) {
     std::lock_guard<std::mutex> lock(mMutex);
 
-    if (mDisplays.count(display) == 0) {
+    auto it = std::find(mDisplays.begin(), mDisplays.end(), display);
+    if (it == mDisplays.end()) {
         mInvalidRefreshCount++;
     }
 
@@ -106,7 +112,8 @@
 Return<void> GraphicsComposerCallback::onVsync_2_4(Display display, int64_t, VsyncPeriodNanos) {
     std::lock_guard<std::mutex> lock(mMutex);
 
-    if (!mVsyncAllowed || mDisplays.count(display) == 0) {
+    auto it = std::find(mDisplays.begin(), mDisplays.end(), display);
+    if (!mVsyncAllowed || it == mDisplays.end()) {
         mInvalidVsync_2_4Count++;
     }
 
@@ -117,7 +124,8 @@
         Display display, const VsyncPeriodChangeTimeline& updatedTimeline) {
     std::lock_guard<std::mutex> lock(mMutex);
 
-    if (mDisplays.count(display) == 0) {
+    auto it = std::find(mDisplays.begin(), mDisplays.end(), display);
+    if (it == mDisplays.end()) {
         mInvalidVsyncPeriodChangeCount++;
     }
 
@@ -134,4 +142,4 @@
     return Void();
 }
 
-}  // namespace android::hardware::graphics::composer::V2_4::vts
\ No newline at end of file
+}  // namespace android::hardware::graphics::composer::V2_4::vts
diff --git a/graphics/composer/2.4/utils/vts/include/composer-vts/2.4/GraphicsComposerCallback.h b/graphics/composer/2.4/utils/vts/include/composer-vts/2.4/GraphicsComposerCallback.h
index f4e23ae..c03070b 100644
--- a/graphics/composer/2.4/utils/vts/include/composer-vts/2.4/GraphicsComposerCallback.h
+++ b/graphics/composer/2.4/utils/vts/include/composer-vts/2.4/GraphicsComposerCallback.h
@@ -18,7 +18,7 @@
 #include <android/hardware/graphics/composer/2.4/IComposerCallback.h>
 
 #include <mutex>
-#include <unordered_set>
+#include <vector>
 
 namespace android::hardware::graphics::composer::V2_4::vts {
 
@@ -56,7 +56,7 @@
 
     mutable std::mutex mMutex;
     // the set of all currently connected displays
-    std::unordered_set<Display> mDisplays;
+    std::vector<Display> mDisplays;
     // true only when vsync is enabled
     bool mVsyncAllowed = true;