diff --git a/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/EnhancedBigtableStubSettings.java b/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/EnhancedBigtableStubSettings.java
index c8c09c484..0bc3b5acc 100644
--- a/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/EnhancedBigtableStubSettings.java
+++ b/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/EnhancedBigtableStubSettings.java
@@ -540,6 +540,7 @@ private Builder() {
           ImmutableMap.<String, String>builder()
               .putAll(
                   BigtableStubSettings.defaultApiClientHeaderProviderBuilder().build().getHeaders())
+              // GrpcHeaderInterceptor treats the `user-agent` as a magic string
               .put(
                   "user-agent",
                   "bigtable-java/"