diff --git a/services/core/java/com/android/server/connectivity/Nat464Xlat.java b/services/core/java/com/android/server/connectivity/Nat464Xlat.java
index 8ad2196..34d0bed 100644
--- a/services/core/java/com/android/server/connectivity/Nat464Xlat.java
+++ b/services/core/java/com/android/server/connectivity/Nat464Xlat.java
@@ -195,6 +195,9 @@
         } catch (ClassCastException | IllegalArgumentException | NullPointerException e) {
             Slog.e(TAG, "Invalid IPv6 address " + addrStr);
         }
+        if (mPrefixDiscoveryRunning && !isPrefixDiscoveryNeeded()) {
+            stopPrefixDiscovery();
+        }
     }
 
     /**
@@ -221,12 +224,11 @@
         if (isPrefixDiscoveryNeeded()) {
             if (!mPrefixDiscoveryRunning) {
                 startPrefixDiscovery();
-            } else {
-                // Prefix discovery is already running. Nothing to do.
-                mState = State.DISCOVERING;
             }
+            mState = State.DISCOVERING;
         } else {
-            stopPrefixDiscovery();  // Enters IDLE state.
+            stopPrefixDiscovery();
+            mState = State.IDLE;
         }
     }
 
@@ -287,7 +289,6 @@
         } catch (RemoteException | ServiceSpecificException e) {
             Slog.e(TAG, "Error starting prefix discovery on netId " + getNetId() + ": " + e);
         }
-        mState = State.DISCOVERING;
         mPrefixDiscoveryRunning = true;
     }
 
@@ -297,7 +298,6 @@
         } catch (RemoteException | ServiceSpecificException e) {
             Slog.e(TAG, "Error stopping prefix discovery on netId " + getNetId() + ": " + e);
         }
-        mState = State.IDLE;
         mPrefixDiscoveryRunning = false;
     }
 
@@ -330,6 +330,7 @@
             case IDLE:
                 if (isPrefixDiscoveryNeeded()) {
                     startPrefixDiscovery();  // Enters DISCOVERING state.
+                    mState = State.DISCOVERING;
                 } else if (requiresClat(mNetwork)) {
                     start();  // Enters STARTING state.
                 }
@@ -344,6 +345,7 @@
                 if (!requiresClat(mNetwork)) {
                     // IPv4 address added. Go back to IDLE state.
                     stopPrefixDiscovery();
+                    mState = State.IDLE;
                     return;
                 }
                 break;
diff --git a/tests/net/java/com/android/server/ConnectivityServiceTest.java b/tests/net/java/com/android/server/ConnectivityServiceTest.java
index c1e51dd..a478e68 100644
--- a/tests/net/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/net/java/com/android/server/ConnectivityServiceTest.java
@@ -6228,6 +6228,22 @@
         inOrder.verify(mMockNetd).clatdStop(iface);
         inOrder.verify(mMockDnsResolver).startPrefix64Discovery(netId);
 
+        // If the RA prefix appears while DNS discovery is in progress, discovery is stopped and
+        // clatd is started with the prefix from the RA.
+        lp.setNat64Prefix(pref64FromRa);
+        mCellNetworkAgent.sendLinkProperties(lp);
+        expectNat64PrefixChange(callback, mCellNetworkAgent, pref64FromRa);
+        inOrder.verify(mMockNetd).clatdStart(iface, pref64FromRa.toString());
+        inOrder.verify(mMockDnsResolver).stopPrefix64Discovery(netId);
+
+        // Withdraw the RA prefix so we can test the case where an RA prefix appears after DNS
+        // discovery has succeeded.
+        lp.setNat64Prefix(null);
+        mCellNetworkAgent.sendLinkProperties(lp);
+        expectNat64PrefixChange(callback, mCellNetworkAgent, null);
+        inOrder.verify(mMockNetd).clatdStop(iface);
+        inOrder.verify(mMockDnsResolver).startPrefix64Discovery(netId);
+
         mService.mNetdEventCallback.onNat64PrefixEvent(netId, true /* added */,
                 pref64FromDnsStr, 96);
         expectNat64PrefixChange(callback, mCellNetworkAgent, pref64FromDns);