diff --git a/src/main/java/org/scribe/builder/ServiceBuilder.java b/src/main/java/org/scribe/builder/ServiceBuilder.java
index 7939287..18f365e 100644
--- a/src/main/java/org/scribe/builder/ServiceBuilder.java
+++ b/src/main/java/org/scribe/builder/ServiceBuilder.java
@@ -101,6 +101,7 @@ public class ServiceBuilder
    */
   public ServiceBuilder scope(String scope)
   {
+    Preconditions.checkEmptyString(scope, "Invalid OAuth scope");
     this.scope = scope;
     return this;
   }