diff --git a/framework/src/android/net/NetworkRequest.java b/framework/src/android/net/NetworkRequest.java
index 5ae25ab..b95363a 100644
--- a/framework/src/android/net/NetworkRequest.java
+++ b/framework/src/android/net/NetworkRequest.java
@@ -32,6 +32,7 @@
 import static android.net.NetworkCapabilities.NET_CAPABILITY_TEMPORARILY_NOT_METERED;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_TRUSTED;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_VALIDATED;
+import static android.net.NetworkCapabilities.RES_ID_UNSET;
 import static android.net.NetworkCapabilities.TRANSPORT_TEST;
 
 import android.annotation.FlaggedApi;
@@ -256,6 +257,9 @@
         if (nc == null) {
             throw new NullPointerException();
         }
+        if (nc.getReservationId() != RES_ID_UNSET) {
+            throw new IllegalArgumentException("ReservationId must only be set by the system");
+        }
         requestId = rId;
         networkCapabilities = nc;
         if (type == Type.RESERVATION) {
diff --git a/tests/cts/net/src/android/net/cts/NetworkRequestTest.java b/tests/cts/net/src/android/net/cts/NetworkRequestTest.java
index 2226f4c..1ca5a77 100644
--- a/tests/cts/net/src/android/net/cts/NetworkRequestTest.java
+++ b/tests/cts/net/src/android/net/cts/NetworkRequestTest.java
@@ -42,6 +42,7 @@
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assume.assumeTrue;
 
@@ -583,4 +584,15 @@
         assertTrue(requestNR.canBeSatisfiedBy(otherSpecificOffer));
         assertTrue(requestNR.canBeSatisfiedBy(regularOffer));
     }
+
+    @Test
+    @IgnoreUpTo(Build.VERSION_CODES.R)
+    public void testNetworkRequest_throwsWhenPassingCapsWithReservationId() {
+        final NetworkCapabilities capsWithResId = new NetworkCapabilities();
+        capsWithResId.setReservationId(42);
+
+        assertThrows(IllegalArgumentException.class, () -> {
+            new NetworkRequest(capsWithResId, TYPE_NONE, 42 /* rId */, NetworkRequest.Type.REQUEST);
+        });
+    }
 }