diff --git a/runtime/src/commonMain/kotlin/com/collectiveidea/twirp/ServiceException.kt b/runtime/src/commonMain/kotlin/com/collectiveidea/twirp/ServiceException.kt
index 1839465..0602689 100644
--- a/runtime/src/commonMain/kotlin/com/collectiveidea/twirp/ServiceException.kt
+++ b/runtime/src/commonMain/kotlin/com/collectiveidea/twirp/ServiceException.kt
@@ -1,6 +1,13 @@
 package com.collectiveidea.twirp
 
+import io.ktor.client.plugins.RedirectResponseException
 import io.ktor.client.plugins.ResponseException
+import io.ktor.http.HttpStatusCode
 
-class ServiceException(val error: ErrorResponse, responseException: ResponseException) :
-    RuntimeException(error.msg, responseException)
+class ServiceException(val error: ErrorResponse, val responseException: ResponseException) :
+    RuntimeException(error.msg, responseException) {
+
+    fun isNotModifiedException(): Boolean {
+        return responseException is RedirectResponseException && responseException.response.status == HttpStatusCode.NotModified
+    }
+}