diff --git a/azure-client-runtime/src/main/java/com/microsoft/azure/TaskGroupBase.java b/azure-client-runtime/src/main/java/com/microsoft/azure/TaskGroupBase.java
index 5078b8caa6..8f178480c4 100644
--- a/azure-client-runtime/src/main/java/com/microsoft/azure/TaskGroupBase.java
+++ b/azure-client-runtime/src/main/java/com/microsoft/azure/TaskGroupBase.java
@@ -165,8 +165,10 @@ public boolean isCancelled() {
          *
          * @param call the call
          */
-        private void addCall(ServiceCall<?> call) {
-            this.serviceCalls.add(call);
+        private void addCall(ServiceCall call) {
+            if (call != null) {
+                this.serviceCalls.add(call);
+            }
         }
     }
 }
diff --git a/build-tools/src/main/resources/checkstyle.xml b/build-tools/src/main/resources/checkstyle.xml
index b7f9348982..d382291b82 100644
--- a/build-tools/src/main/resources/checkstyle.xml
+++ b/build-tools/src/main/resources/checkstyle.xml
@@ -79,11 +79,6 @@
         <property name="eachLine" value="true"/>
     </module>
 
-    <module name="RegexpSingleline">
-        <property name="format" value="\s+$"/>
-        <property name="message" value="Line has trailing spaces."/>
-    </module>
-
     <module name="TreeWalker">
         <!-- Checks for Javadoc comments.                     -->
         <!-- See http://checkstyle.sf.net/config_javadoc.html -->