diff --git a/service/src/com/android/server/connectivity/ClatCoordinator.java b/service/src/com/android/server/connectivity/ClatCoordinator.java
index 7616457..c57983b 100644
--- a/service/src/com/android/server/connectivity/ClatCoordinator.java
+++ b/service/src/com/android/server/connectivity/ClatCoordinator.java
@@ -220,7 +220,7 @@
             @NonNull final IpPrefix nat64Prefix)
             throws IOException {
         if (mIface != null || mPid != INVALID_PID) {
-            throw new IOException("Clatd has started on " + mIface + " (pid " + mPid + ")");
+            throw new IOException("Clatd is already running on " + mIface + " (pid " + mPid + ")");
         }
         if (nat64Prefix.getPrefixLength() != 96) {
             throw new IOException("Prefix must be 96 bits long: " + nat64Prefix);
diff --git a/tests/unit/java/com/android/server/connectivity/ClatCoordinatorTest.java b/tests/unit/java/com/android/server/connectivity/ClatCoordinatorTest.java
index bdcc21b..84e02ce 100644
--- a/tests/unit/java/com/android/server/connectivity/ClatCoordinatorTest.java
+++ b/tests/unit/java/com/android/server/connectivity/ClatCoordinatorTest.java
@@ -340,7 +340,7 @@
         inOrder.verifyNoMoreInteractions();
 
         // [2] Start clatd again failed.
-        assertThrows("java.io.IOException: Clatd has started on test0 (pid 10483)",
+        assertThrows("java.io.IOException: Clatd is already running on test0 (pid 10483)",
                 IOException.class,
                 () -> coordinator.clatStart(BASE_IFACE, NETID, NAT64_IP_PREFIX));