diff --git a/services/inputflinger/InputReader.cpp b/services/inputflinger/InputReader.cpp
index 5d0b894..75095cb 100644
--- a/services/inputflinger/InputReader.cpp
+++ b/services/inputflinger/InputReader.cpp
@@ -254,7 +254,6 @@
 }
 
 
-
 // --- InputReader ---
 
 InputReader::InputReader(const sp<EventHubInterface>& eventHub,
@@ -3446,7 +3445,17 @@
         } else {
             viewportTypeToUse = ViewportType::VIEWPORT_INTERNAL;
         }
-        return mConfig.getDisplayViewportByType(viewportTypeToUse);
+
+        std::optional<DisplayViewport> viewport =
+                mConfig.getDisplayViewportByType(viewportTypeToUse);
+        if (!viewport && viewportTypeToUse == ViewportType::VIEWPORT_EXTERNAL) {
+            ALOGW("Input device %s should be associated with external display, "
+                    "fallback to internal one for the external viewport is not found.",
+                        getDeviceName().c_str());
+            viewport = mConfig.getDisplayViewportByType(ViewportType::VIEWPORT_INTERNAL);
+        }
+
+        return viewport;
     }
 
     DisplayViewport newViewport;
diff --git a/services/inputflinger/tests/InputReader_test.cpp b/services/inputflinger/tests/InputReader_test.cpp
index 167a624..b5d2090 100644
--- a/services/inputflinger/tests/InputReader_test.cpp
+++ b/services/inputflinger/tests/InputReader_test.cpp
@@ -6284,4 +6284,34 @@
     ASSERT_EQ(DISPLAY_ID, args.displayId);
 }
 
+/**
+ * Expect fallback to internal viewport if device is external and external viewport is not present.
+ */
+TEST_F(MultiTouchInputMapperTest, Viewports_Fallback) {
+    MultiTouchInputMapper* mapper = new MultiTouchInputMapper(mDevice);
+    prepareAxes(POSITION);
+    addConfigurationProperty("touch.deviceType", "touchScreen");
+    prepareDisplay(DISPLAY_ORIENTATION_0);
+    mDevice->setExternal(true);
+    addMapperAndConfigure(mapper);
+
+    ASSERT_EQ(AINPUT_SOURCE_TOUCHSCREEN, mapper->getSources());
+
+    NotifyMotionArgs motionArgs;
+
+    // Expect the event to be sent to the internal viewport,
+    // because an external viewport is not present.
+    processPosition(mapper, 100, 100);
+    processSync(mapper);
+    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(&motionArgs));
+    ASSERT_EQ(ADISPLAY_ID_DEFAULT, motionArgs.displayId);
+
+    // Expect the event to be sent to the external viewport if it is present.
+    prepareSecondaryDisplay(ViewportType::VIEWPORT_EXTERNAL);
+    processPosition(mapper, 100, 100);
+    processSync(mapper);
+    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(&motionArgs));
+    ASSERT_EQ(SECONDARY_DISPLAY_ID, motionArgs.displayId);
+}
+
 } // namespace android