diff --git a/pom.xml b/pom.xml
index b9b8d010e3..acb03cd111 100644
--- a/pom.xml
+++ b/pom.xml
@@ -86,7 +86,7 @@
     <dep.opentest4j.version>1.3.0</dep.opentest4j.version>
     <dep.picocli.version>4.7.7</dep.picocli.version>
     <dep.proto-google-common-protos.version>2.63.1</dep.proto-google-common-protos.version>
-    <dep.protobuf.version>3.25.5</dep.protobuf.version>
+    <dep.protobuf.version>4.33.0</dep.protobuf.version>
     <dep.resilience4j.version>1.7.0</dep.resilience4j.version>
     <dep.slf4j.version>2.0.17</dep.slf4j.version>
     <dep.spymemcached.version>2.12.3</dep.spymemcached.version>
diff --git a/src/main/java/emissary/grpc/GrpcRoutingPlace.java b/src/main/java/emissary/grpc/GrpcRoutingPlace.java
index 413fed5762..e4020c346d 100644
--- a/src/main/java/emissary/grpc/GrpcRoutingPlace.java
+++ b/src/main/java/emissary/grpc/GrpcRoutingPlace.java
@@ -9,7 +9,7 @@
 import emissary.place.ServiceProviderPlace;
 
 import com.google.common.util.concurrent.ListenableFuture;
-import com.google.protobuf.GeneratedMessageV3;
+import com.google.protobuf.Message;
 import io.grpc.ManagedChannel;
 import io.grpc.StatusRuntimeException;
 import io.grpc.stub.AbstractBlockingStub;
@@ -170,8 +170,8 @@ protected void passivateConnection(ManagedChannel managedChannel) { /* No-op */
      * @param <R> the protobuf response type
      * @param <S> the gRPC stub type
      */
-    protected <Q extends GeneratedMessageV3, R extends GeneratedMessageV3, S extends AbstractBlockingStub<S>> R invokeGrpc(
-            String targetId, Function<ManagedChannel, S> stubFactory, BiFunction<S, Q, R> callLogic, Q request) {
+    protected <Q extends Message, R extends Message, S extends AbstractBlockingStub<S>> R invokeGrpc(String targetId,
+            Function<ManagedChannel, S> stubFactory, BiFunction<S, Q, R> callLogic, Q request) {
 
         return retryHandler.execute(() -> {
             ObjectPool<ManagedChannel> channelPool = channelPoolLookup(targetId);
@@ -207,9 +207,8 @@ protected <Q extends GeneratedMessageV3, R extends GeneratedMessageV3, S extends
      * @param <R> the protobuf response type
      * @param <S> the gRPC stub type
      */
-    protected <Q extends GeneratedMessageV3, R extends GeneratedMessageV3, S extends AbstractFutureStub<S>> List<R> invokeBatchedGrpc(
-            String targetId, Function<ManagedChannel, S> stubFactory,
-            BiFunction<S, Q, ListenableFuture<R>> callLogic, List<Q> requestList) {
+    protected <Q extends Message, R extends Message, S extends AbstractFutureStub<S>> List<R> invokeBatchedGrpc(String targetId,
+            Function<ManagedChannel, S> stubFactory, BiFunction<S, Q, ListenableFuture<R>> callLogic, List<Q> requestList) {
 
         throw new UnsupportedOperationException("Not yet implemented");
     }
diff --git a/src/main/java/emissary/grpc/sample/GrpcSampleServicePlace.java b/src/main/java/emissary/grpc/sample/GrpcSampleServicePlace.java
index 412ab21fb8..9f2b2a839e 100644
--- a/src/main/java/emissary/grpc/sample/GrpcSampleServicePlace.java
+++ b/src/main/java/emissary/grpc/sample/GrpcSampleServicePlace.java
@@ -96,7 +96,11 @@ private void processWithMockBehavior(
             SampleRequest request = SampleRequest.newBuilder()
                     .setQuery(ByteString.copyFrom(o.data()))
                     .build();
-            SampleResponse response = invokeGrpc(targetId, SampleServiceGrpc::newBlockingStub, callLogic, request);
+            SampleResponse response = invokeGrpc(
+                    targetId,
+                    SampleServiceGrpc::newBlockingStub, // or: (ManagedChannel c) -> SampleServiceGrpc.newBlockingStub(c)
+                    callLogic,
+                    request);
             o.addAlternateView(ALTERNATE_VIEW_NAME, response.getResult().toByteArray());
         }
     }