diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Assignee.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Assignee.java
index f1489bbe15..7d6b1c3f81 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Assignee.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Assignee.java
@@ -113,6 +113,8 @@ public class Assignee extends Composite {
     if (currentAssignee != null) {
       suggestBox.setText(FormatUtil.nameEmail(currentAssignee));
       suggestBox.selectAll();
+    } else {
+      suggestBox.setText("");
     }
   }
 
@@ -137,7 +139,7 @@ public class Assignee extends Composite {
   }
 
   private void editAssignee(final String assignee) {
-    if (assignee.isEmpty()) {
+    if (assignee.trim().isEmpty()) {
       ChangeApi.deleteAssignee(changeId.get(),
           new GerritCallback<AccountInfo>() {
             @Override
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/PutAssignee.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/PutAssignee.java
index 50024362ca..d377cade63 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/PutAssignee.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/PutAssignee.java
@@ -14,7 +14,6 @@
 
 package com.google.gerrit.server.change;
 
-import com.google.common.base.Strings;
 import com.google.gerrit.common.TimeUtil;
 import com.google.gerrit.extensions.api.changes.AddReviewerInput;
 import com.google.gerrit.extensions.api.changes.AssigneeInput;
@@ -65,7 +64,7 @@ public class PutAssignee implements
     if (!rsrc.getControl().canEditAssignee()) {
       throw new AuthException("Changing Assignee not permitted");
     }
-    if (Strings.isNullOrEmpty(input.assignee)) {
+    if (input.assignee == null || input.assignee.trim().isEmpty()) {
       throw new BadRequestException("missing assignee field");
     }