diff --git a/res/values/strings.xml b/res/values/strings.xml
index f5db225..c42e0cd 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -838,7 +838,7 @@
     <!-- FDN settings: error message displayed in a popup (toast) -->
     <string name="pin2_invalid">FDN wasn\'t updated because you typed an incorrect PIN.</string>
     <!-- FDN settings: error message displayed in a popup (toast) -->
-    <string name="fdn_invalid_number">FDN wasn\'t updated because the number can\'t exceed 20 digits.</string>
+    <string name="fdn_invalid_number">FDN wasn\'t updated because the number is empty or exceeds 20 digits.</string>
     <!-- FDN settings: error message displayed in a popup (toast), when the entered
          FDN number was inappropriate, OR, PIN2 the user entered was incorrect.
          Because of API restriction, there's no way to determine which is the exact
diff --git a/src/com/android/phone/settings/fdn/EditFdnContactScreen.java b/src/com/android/phone/settings/fdn/EditFdnContactScreen.java
index 1387215..23ef0bb 100644
--- a/src/com/android/phone/settings/fdn/EditFdnContactScreen.java
+++ b/src/com/android/phone/settings/fdn/EditFdnContactScreen.java
@@ -281,7 +281,7 @@
       * TODO: Fix this logic.
       */
      private boolean isValidNumber(String number) {
-         return (number.length() <= 20);
+         return (number.length() <= 20) && (number.length() > 0);
      }
 
 
@@ -419,6 +419,12 @@
             } else if (v == mNumberField) {
                 mButton.requestFocus();
             } else if (v == mButton) {
+                final String number = PhoneNumberUtils.convertAndStrip(getNumberFromTextField());
+
+                if (!isValidNumber(number)) {
+                    handleResult(false, true);
+                    return;
+                }
                 // Authenticate the pin AFTER the contact information
                 // is entered, and if we're not busy.
                 if (!mDataBusy) {