diff --git a/src/com/fsck/k9/mail/Message.java b/src/com/fsck/k9/mail/Message.java
index ce1a59711..d09c7b1a3 100644
--- a/src/com/fsck/k9/mail/Message.java
+++ b/src/com/fsck/k9/mail/Message.java
@@ -5,6 +5,7 @@ import java.io.IOException;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
+import java.util.EnumSet;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -27,7 +28,7 @@ public abstract class Message implements Part, CompositeBody {
 
     protected String mUid;
 
-    private Set<Flag> mFlags = new HashSet<Flag>();
+    private Set<Flag> mFlags = EnumSet.noneOf(Flag.class);
 
     private Date mInternalDate;
 
@@ -291,7 +292,7 @@ public abstract class Message implements Part, CompositeBody {
         destination.mReference = mReference;
 
         // mFlags contents can change during the object lifetime, so copy the Set
-        destination.mFlags = new HashSet<Flag>(mFlags);
+        destination.mFlags = EnumSet.copyOf(mFlags);
     }
 
     /**
diff --git a/src/com/fsck/k9/mail/store/ImapStore.java b/src/com/fsck/k9/mail/store/ImapStore.java
index 291f1d768..acfe04aa2 100644
--- a/src/com/fsck/k9/mail/store/ImapStore.java
+++ b/src/com/fsck/k9/mail/store/ImapStore.java
@@ -30,6 +30,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
 import java.util.Deque;
+import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
@@ -116,7 +117,7 @@ public class ImapStore extends Store {
 
     private static int FETCH_WINDOW_SIZE = 100;
 
-    private Set<Flag> mPermanentFlagsIndex = new HashSet<Flag>();
+    private Set<Flag> mPermanentFlagsIndex = EnumSet.noneOf(Flag.class);
 
     private static final String CAPABILITY_IDLE = "IDLE";
     private static final String CAPABILITY_AUTH_CRAM_MD5 = "AUTH=CRAM-MD5";