diff --git a/services/core/java/com/android/server/policy/PhoneWindowManager.java b/services/core/java/com/android/server/policy/PhoneWindowManager.java
index 247a5c02452e8..b43fceef750fc 100644
--- a/services/core/java/com/android/server/policy/PhoneWindowManager.java
+++ b/services/core/java/com/android/server/policy/PhoneWindowManager.java
@@ -3091,18 +3091,21 @@ public class PhoneWindowManager implements WindowManagerPolicy {
                     }
                     int screenDisplayId = displayId < 0 ? DEFAULT_DISPLAY : displayId;
 
+                    float minLinearBrightness = mPowerManager.getBrightnessConstraint(
+                            PowerManager.BRIGHTNESS_CONSTRAINT_TYPE_MINIMUM);
+                    float maxLinearBrightness = mPowerManager.getBrightnessConstraint(
+                            PowerManager.BRIGHTNESS_CONSTRAINT_TYPE_MAXIMUM);
                     float linearBrightness = mDisplayManager.getBrightness(screenDisplayId);
 
                     float gammaBrightness = BrightnessUtils.convertLinearToGamma(linearBrightness);
                     float adjustedGammaBrightness =
                             gammaBrightness + 1f / BRIGHTNESS_STEPS * direction;
-
+                    adjustedGammaBrightness = MathUtils.constrain(adjustedGammaBrightness, 0f,
+                            1f);
                     float adjustedLinearBrightness = BrightnessUtils.convertGammaToLinear(
                             adjustedGammaBrightness);
-
-                    adjustedLinearBrightness = MathUtils.constrain(adjustedLinearBrightness, 0f,
-                            1f);
-
+                    adjustedLinearBrightness = MathUtils.constrain(adjustedLinearBrightness,
+                            minLinearBrightness, maxLinearBrightness);
                     mDisplayManager.setBrightness(screenDisplayId, adjustedLinearBrightness);
 
                     startActivityAsUser(new Intent(Intent.ACTION_SHOW_BRIGHTNESS_DIALOG),
diff --git a/services/tests/wmtests/src/com/android/server/policy/ModifierShortcutTests.java b/services/tests/wmtests/src/com/android/server/policy/ModifierShortcutTests.java
index bf6901e963e0d..9029bc48138ca 100644
--- a/services/tests/wmtests/src/com/android/server/policy/ModifierShortcutTests.java
+++ b/services/tests/wmtests/src/com/android/server/policy/ModifierShortcutTests.java
@@ -18,6 +18,7 @@ package com.android.server.policy;
 
 import static android.view.KeyEvent.KEYCODE_ALT_LEFT;
 import static android.view.KeyEvent.KEYCODE_B;
+import static android.view.KeyEvent.KEYCODE_BRIGHTNESS_DOWN;
 import static android.view.KeyEvent.KEYCODE_C;
 import static android.view.KeyEvent.KEYCODE_CTRL_LEFT;
 import static android.view.KeyEvent.KEYCODE_E;
@@ -186,4 +187,19 @@ public class ModifierShortcutTests extends ShortcutKeyTestBase {
         sendKeyCombination(new int[]{KEYCODE_META_LEFT, KEYCODE_ENTER}, 0);
         mPhoneWindowManager.assertGoToHomescreen();
     }
+
+    /**
+     * Sends a KEYCODE_BRIGHTNESS_DOWN event and validates the brightness is decreased as expected;
+     */
+    @Test
+    public void testKeyCodeBrightnessDown() {
+        float[] currentBrightness = new float[]{0.1f, 0.05f, 0.0f};
+        float[] newBrightness = new float[]{0.065738f, 0.0275134f, 0.0f};
+
+        for (int i = 0; i < currentBrightness.length; i++) {
+            mPhoneWindowManager.prepareBrightnessDecrease(currentBrightness[i]);
+            sendKey(KEYCODE_BRIGHTNESS_DOWN);
+            mPhoneWindowManager.verifyNewBrightness(newBrightness[i]);
+        }
+    }
 }
diff --git a/services/tests/wmtests/src/com/android/server/policy/TestPhoneWindowManager.java b/services/tests/wmtests/src/com/android/server/policy/TestPhoneWindowManager.java
index 2665e197f91f2..f2d71bd7c7a73 100644
--- a/services/tests/wmtests/src/com/android/server/policy/TestPhoneWindowManager.java
+++ b/services/tests/wmtests/src/com/android/server/policy/TestPhoneWindowManager.java
@@ -88,6 +88,7 @@ import com.android.server.wm.WindowManagerInternal.AppTransitionListener;
 
 import junit.framework.Assert;
 
+import org.mockito.AdditionalMatchers;
 import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
 import org.mockito.MockSettings;
@@ -330,6 +331,20 @@ class TestPhoneWindowManager {
         setPhoneCallIsInProgress();
     }
 
+    void prepareBrightnessDecrease(float currentBrightness) {
+        doReturn(0.0f).when(mPowerManager)
+                .getBrightnessConstraint(PowerManager.BRIGHTNESS_CONSTRAINT_TYPE_MINIMUM);
+        doReturn(1.0f).when(mPowerManager)
+                .getBrightnessConstraint(PowerManager.BRIGHTNESS_CONSTRAINT_TYPE_MAXIMUM);
+        doReturn(currentBrightness).when(mDisplayManager)
+                .getBrightness(0);
+    }
+
+    void verifyNewBrightness(float newBrightness) {
+        verify(mDisplayManager).setBrightness(Mockito.eq(0),
+                AdditionalMatchers.eq(newBrightness, 0.001f));
+    }
+
     void setPhoneCallIsInProgress() {
         // Let device has an ongoing phone call.
         doReturn(false).when(mTelecomManager).isRinging();