diff --git a/google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java b/google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java
index a008bb602ffa..f051e351beab 100644
--- a/google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java
+++ b/google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java
@@ -43,7 +43,7 @@
 public class SpannerOptions extends ServiceOptions<Spanner, SpannerOptions> {
   private static final String API_SHORT_NAME = "Spanner";
   private static final String DEFAULT_HOST = "https://spanner.googleapis.com";
-  private static final Set<String> SCOPES =
+  private static final ImmutableSet<String> SCOPES =
       ImmutableSet.of(
           "https://www.googleapis.com/auth/spanner.admin",
           "https://www.googleapis.com/auth/spanner.data");