diff --git a/webapp/src/edu/cornell/mannlib/vitro/webapp/auth/identifier/common/AbstractCommonIdentifier.java b/webapp/src/edu/cornell/mannlib/vitro/webapp/auth/identifier/common/AbstractCommonIdentifier.java
index 969131c20..5b7d95948 100644
--- a/webapp/src/edu/cornell/mannlib/vitro/webapp/auth/identifier/common/AbstractCommonIdentifier.java
+++ b/webapp/src/edu/cornell/mannlib/vitro/webapp/auth/identifier/common/AbstractCommonIdentifier.java
@@ -3,6 +3,7 @@
 package edu.cornell.mannlib.vitro.webapp.auth.identifier.common;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -14,8 +15,16 @@ import edu.cornell.mannlib.vitro.webapp.auth.identifier.IdentifierBundle;
  * CommonIdentifierBundleFactory.
  */
 public abstract class AbstractCommonIdentifier {
-	protected static <T> Collection<T> getIdentifiersForClass(
+
+	/**
+	 * Get all of the instances of this class of Identifier from this bundle.
+	 */
+	protected static <T extends Identifier> Collection<T> getIdentifiersForClass(
 			IdentifierBundle ids, Class<T> clazz) {
+		if ((ids == null) || (clazz == null)) {
+			return Collections.emptySet();
+		}
+
 		Set<T> set = new HashSet<T>();
 		for (Identifier id : ids) {
 			if (clazz.isAssignableFrom(id.getClass())) {