diff --git a/common/build.gradle b/common/build.gradle
index 9a01a80b83..3aeb644d42 100644
--- a/common/build.gradle
+++ b/common/build.gradle
@@ -36,11 +36,11 @@ jacocoTestCoverageVerification {
         rule {
             limit {
                 counter = 'LINE'
-                minimum = 0.6 //TODO: add more test to meet the coverage bar 0.9
+                minimum = 0.8 //TODO: add more test to meet the coverage bar 0.9
             }
             limit {
                 counter = 'BRANCH'
-                minimum = 0.5 //TODO: add more test to meet the coverage bar 0.9
+                minimum = 0.7 //TODO: add more test to meet the coverage bar 0.9
             }
         }
     }
diff --git a/common/src/main/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorInput.java b/common/src/main/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorInput.java
index aec2d1b0b6..43568afb05 100644
--- a/common/src/main/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorInput.java
+++ b/common/src/main/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorInput.java
@@ -227,7 +227,7 @@ public void writeTo(StreamOutput output) throws IOException {
         }
         if (!CollectionUtils.isEmpty(backendRoles)) {
             output.writeBoolean(true);
-            output.writeOptionalStringCollection(backendRoles);
+            output.writeStringCollection(backendRoles);
         } else {
             output.writeBoolean(false);
         }
diff --git a/common/src/test/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorInputTests.java b/common/src/test/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorInputTests.java
index 4de9198785..81a6e36b64 100644
--- a/common/src/test/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorInputTests.java
+++ b/common/src/test/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorInputTests.java
@@ -7,6 +7,7 @@
 
 import java.io.IOException;
 import java.io.UncheckedIOException;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -42,7 +43,6 @@ public void setUp(){
         String postProcessFunction = MLPostProcessFunction.OPENAI_EMBEDDING;
         ConnectorAction action = new ConnectorAction(actionType, method, url, headers, mlCreateConnectorRequestBody, preProcessFunction, postProcessFunction);
 
-        // java.lang.IllegalStateException: unexpected byte [0x6f] will be thrown if we specify backendRoles field.
         mlCreateConnectorInput = MLCreateConnectorInput.builder()
                 .name("test_connector_name")
                 .description("this is a test connector")
@@ -52,7 +52,8 @@ public void setUp(){
                 .credential(Map.of("key", "test_key_value"))
                 .actions(List.of(action))
                 .access(AccessMode.PUBLIC)
-                .addAllBackendRoles(true)
+                .backendRoles(Arrays.asList("role1", "role2"))
+                .addAllBackendRoles(false)
                 .build();
     }
 
diff --git a/common/src/test/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorRequestTests.java b/common/src/test/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorRequestTests.java
index 581a4bdf33..6fe82d7f2b 100644
--- a/common/src/test/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorRequestTests.java
+++ b/common/src/test/java/org/opensearch/ml/common/transport/connector/MLCreateConnectorRequestTests.java
@@ -7,6 +7,7 @@
 
 import java.io.IOException;
 import java.io.UncheckedIOException;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -52,7 +53,8 @@ public void setUp(){
                 .credential(Map.of("key", "test_key_value"))
                 .actions(List.of(action))
                 .access(AccessMode.PUBLIC)
-                .addAllBackendRoles(true)
+                .backendRoles(Arrays.asList("role1", "role2"))
+                .addAllBackendRoles(false)
                 .build();
     }