diff --git a/retrofit/build.gradle b/retrofit/build.gradle
index 280fea55c8..7aa4c2d362 100644
--- a/retrofit/build.gradle
+++ b/retrofit/build.gradle
@@ -47,6 +47,9 @@ dependencies {
 
   // Can't extend extraCompileOnly from compileOnly due to the circular dependencies.
   extraCompileOnly libs.okhttp.client
+
+  // Allow types in the main source set to be visible to the extra source set.
+  extraImplementation sourceSets.main.output
 }
 
 javadoc {