diff --git a/include/grpc++/impl/codegen/call.h b/include/grpc++/impl/codegen/call.h
index e245eed0040..c4167826b60 100644
--- a/include/grpc++/impl/codegen/call.h
+++ b/include/grpc++/impl/codegen/call.h
@@ -245,8 +245,10 @@ class CallOpSendInitialMetadata {
     op->data.send_initial_metadata.metadata = initial_metadata_;
     op->data.send_initial_metadata.maybe_compression_level.is_set =
         maybe_compression_level_.is_set;
-    op->data.send_initial_metadata.maybe_compression_level.level =
-        maybe_compression_level_.level;
+    if (maybe_compression_level_.is_set) {
+      op->data.send_initial_metadata.maybe_compression_level.level =
+          maybe_compression_level_.level;
+    }
   }
   void FinishOp(bool* status) {
     if (!send_) return;
diff --git a/third_party/zlib b/third_party/zlib
index cacf7f1d4e3..50893291621 160000
--- a/third_party/zlib
+++ b/third_party/zlib
@@ -1 +1 @@
-Subproject commit cacf7f1d4e3d44d871b605da3b647f07d718623f
+Subproject commit 50893291621658f355bc5b4d450a8d06a563053d