diff --git a/google-cloud-pubsublite/pom.xml b/google-cloud-pubsublite/pom.xml
index 2be7e9b97..73857875e 100644
--- a/google-cloud-pubsublite/pom.xml
+++ b/google-cloud-pubsublite/pom.xml
@@ -89,6 +89,17 @@
       <groupId>com.google.api</groupId>
       <artifactId>gax-grpc</artifactId>
     </dependency>
+    <dependency>
+      <groupId>com.google.code.gson</groupId>
+      <artifactId>gson</artifactId>
+      <!--
+       Within this repository this dependency is only used in tests. However,
+       making this test scope causes undeclared dependencies after the
+       flatten-maven-plugin.
+       https://github.com/mojohaus/flatten-maven-plugin/issues/185
+      -->
+      <scope>runtime</scope>
+    </dependency>
     <dependency>
       <groupId>io.grpc</groupId>
       <artifactId>grpc-protobuf</artifactId>
@@ -129,11 +140,6 @@
       <version>2.2</version>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>com.google.code.gson</groupId>
-      <artifactId>gson</artifactId>
-      <scope>test</scope>
-    </dependency>
     <dependency>
       <groupId>com.google.guava</groupId>
       <artifactId>guava-testlib</artifactId>