diff --git a/okhttp/src/main/java/io/grpc/okhttp/Headers.java b/okhttp/src/main/java/io/grpc/okhttp/Headers.java
index 544647ca06..e532b6ea3b 100644
--- a/okhttp/src/main/java/io/grpc/okhttp/Headers.java
+++ b/okhttp/src/main/java/io/grpc/okhttp/Headers.java
@@ -46,8 +46,6 @@ import okio.ByteString;
 import java.util.ArrayList;
 import java.util.List;
 
-import javax.annotation.Nullable;
-
 /**
  * Constants for request/response headers.
  */
@@ -65,7 +63,7 @@ public class Headers {
    * application thread context.
    */
   public static List<Header> createRequestHeaders(Metadata headers, String defaultPath,
-      String authority, @Nullable String applicationUserAgent) {
+      String authority, String userAgent) {
     Preconditions.checkNotNull(headers, "headers");
     Preconditions.checkNotNull(defaultPath, "defaultPath");
     Preconditions.checkNotNull(authority, "authority");
@@ -81,7 +79,6 @@ public class Headers {
     String path = defaultPath;
     okhttpHeaders.add(new Header(Header.TARGET_PATH, path));
 
-    String userAgent = GrpcUtil.getGrpcUserAgent("okhttp", applicationUserAgent);
     okhttpHeaders.add(new Header(GrpcUtil.USER_AGENT_KEY.name(), userAgent));
 
     // All non-pseudo headers must come after pseudo headers.
diff --git a/okhttp/src/main/java/io/grpc/okhttp/OkHttpClientStream.java b/okhttp/src/main/java/io/grpc/okhttp/OkHttpClientStream.java
index 76af89ef9e..22f5aa6c31 100644
--- a/okhttp/src/main/java/io/grpc/okhttp/OkHttpClientStream.java
+++ b/okhttp/src/main/java/io/grpc/okhttp/OkHttpClientStream.java
@@ -96,7 +96,7 @@ class OkHttpClientStream extends Http2ClientStream {
       Object lock,
       int maxMessageSize,
       String authority,
-      @Nullable String userAgent) {
+      String userAgent) {
     super(new OkHttpWritableBufferAllocator(), maxMessageSize);
     this.method = method;
     this.headers = headers;
diff --git a/okhttp/src/main/java/io/grpc/okhttp/OkHttpClientTransport.java b/okhttp/src/main/java/io/grpc/okhttp/OkHttpClientTransport.java
index 465ff6e04e..6d1a7fa33b 100644
--- a/okhttp/src/main/java/io/grpc/okhttp/OkHttpClientTransport.java
+++ b/okhttp/src/main/java/io/grpc/okhttp/OkHttpClientTransport.java
@@ -183,7 +183,7 @@ class OkHttpClientTransport implements ManagedClientTransport {
     this.sslSocketFactory = sslSocketFactory;
     this.connectionSpec = Preconditions.checkNotNull(connectionSpec, "connectionSpec");
     this.ticker = Ticker.systemTicker();
-    this.userAgent = userAgent;
+    this.userAgent = GrpcUtil.getGrpcUserAgent("okhttp", userAgent);
   }
 
   /**
@@ -197,7 +197,7 @@ class OkHttpClientTransport implements ManagedClientTransport {
     address = null;
     this.maxMessageSize = maxMessageSize;
     defaultAuthority = "notarealauthority:80";
-    this.userAgent = userAgent;
+    this.userAgent = GrpcUtil.getGrpcUserAgent("okhttp", userAgent);
     this.executor = Preconditions.checkNotNull(executor);
     serializingExecutor = new SerializingExecutor(executor);
     this.testFrameReader = Preconditions.checkNotNull(frameReader);