diff --git a/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceClient.java b/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceClient.java
index 1e555f5..38a4aa6 100644
--- a/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceClient.java
+++ b/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceClient.java
@@ -338,6 +338,8 @@
           } catch (Exception e) {
             throw new RuntimeException(e);
           }
+        } else {
+          builder.usePlaintext(true);
         }
         return builder.build();
       }