diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/AccessSectionEditor.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/AccessSectionEditor.java
index e518d26..1b946cd 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/AccessSectionEditor.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/AccessSectionEditor.java
@@ -169,7 +169,7 @@
 
   @Override
   public void setValue(AccessSection value) {
-    Collections.sort(value.getPermissions());
+    sortPermissions(value);
 
     this.value = value;
     this.readOnly = !editing || !(projectAccess.isOwnerOf(value) || projectAccess.canUpload());
@@ -204,6 +204,12 @@
     }
   }
 
+  private void sortPermissions(AccessSection accessSection) {
+    List<Permission> permissionList = new ArrayList<>(accessSection.getPermissions());
+    Collections.sort(permissionList);
+    accessSection.setPermissions(permissionList);
+  }
+
   void setEditing(boolean editing) {
     this.editing = editing;
   }
diff --git a/java/com/google/gerrit/common/data/AccessSection.java b/java/com/google/gerrit/common/data/AccessSection.java
index b525f4d..ce47881 100644
--- a/java/com/google/gerrit/common/data/AccessSection.java
+++ b/java/com/google/gerrit/common/data/AccessSection.java
@@ -34,11 +34,12 @@
     super(refPattern);
   }
 
+  // TODO(ekempin): Make this method return an ImmutableList once the GWT UI is gone.
   public List<Permission> getPermissions() {
     if (permissions == null) {
-      permissions = new ArrayList<>();
+      return new ArrayList<>();
     }
-    return permissions;
+    return new ArrayList<>(permissions);
   }
 
   public void setPermissions(List<Permission> list) {
@@ -59,13 +60,19 @@
 
   @Nullable
   public Permission getPermission(String name, boolean create) {
-    for (Permission p : getPermissions()) {
-      if (p.getName().equalsIgnoreCase(name)) {
-        return p;
+    if (permissions != null) {
+      for (Permission p : permissions) {
+        if (p.getName().equalsIgnoreCase(name)) {
+          return p;
+        }
       }
     }
 
     if (create) {
+      if (permissions == null) {
+        permissions = new ArrayList<>();
+      }
+
       Permission p = new Permission(name);
       permissions.add(p);
       return p;
@@ -75,7 +82,10 @@
   }
 
   public void addPermission(Permission permission) {
-    List<Permission> permissions = getPermissions();
+    if (permissions == null) {
+      permissions = new ArrayList<>();
+    }
+
     for (Permission p : permissions) {
       if (p.getName().equalsIgnoreCase(permission.getName())) {
         throw new IllegalArgumentException();
diff --git a/java/com/google/gerrit/server/restapi/project/SetAccessUtil.java b/java/com/google/gerrit/server/restapi/project/SetAccessUtil.java
index 422c749..c5c8cf0 100644
--- a/java/com/google/gerrit/server/restapi/project/SetAccessUtil.java
+++ b/java/com/google/gerrit/server/restapi/project/SetAccessUtil.java
@@ -115,7 +115,7 @@
           }
           p.add(r);
         }
-        accessSection.getPermissions().add(p);
+        accessSection.addPermission(p);
       }
       sections.add(accessSection);
     }
diff --git a/javatests/com/google/gerrit/common/data/AccessSectionTest.java b/javatests/com/google/gerrit/common/data/AccessSectionTest.java
index 61ee6c9..ecdb3c8 100644
--- a/javatests/com/google/gerrit/common/data/AccessSectionTest.java
+++ b/javatests/com/google/gerrit/common/data/AccessSectionTest.java
@@ -127,7 +127,7 @@
   }
 
   @Test
-  public void cannotAddPermissionByModifyingList() {
+  public void cannotAddPermissionByModifyingListThatWasProvidedToAccessSection() {
     Permission abandonPermission = new Permission(Permission.ABANDON);
     Permission rebasePermission = new Permission(Permission.REBASE);
 
@@ -143,6 +143,21 @@
   }
 
   @Test
+  public void cannotAddPermissionByModifyingListThatWasRetrievedFromAccessSection() {
+    Permission submitPermission = new Permission(Permission.SUBMIT);
+    accessSection.getPermissions().add(submitPermission);
+    assertThat(accessSection.getPermission(Permission.SUBMIT)).isNull();
+
+    List<Permission> permissions = new ArrayList<>();
+    permissions.add(new Permission(Permission.ABANDON));
+    permissions.add(new Permission(Permission.REBASE));
+    accessSection.setPermissions(permissions);
+    assertThat(accessSection.getPermission(Permission.SUBMIT)).isNull();
+    accessSection.getPermissions().add(submitPermission);
+    assertThat(accessSection.getPermission(Permission.SUBMIT)).isNull();
+  }
+
+  @Test
   public void removePermission() {
     Permission abandonPermission = new Permission(Permission.ABANDON);
     Permission rebasePermission = new Permission(Permission.REBASE);