diff --git a/src/engine/imap/api/imap-folder-session.vala b/src/engine/imap/api/imap-folder-session.vala
index bf4cd2bc..d544b3b5 100644
--- a/src/engine/imap/api/imap-folder-session.vala
+++ b/src/engine/imap/api/imap-folder-session.vala
@@ -661,7 +661,7 @@ private class Geary.Imap.FolderSession : Geary.Imap.SessionObject {
                 all_uid = false;
 
             cmds.add(
-                new StoreCommand(msg_set, flags, StoreCommand.Option.ADD_FLAGS, cancellable)
+                new StoreCommand(msg_set, ADD_FLAGS, SILENT, flags, cancellable)
             );
         }
 
@@ -698,7 +698,11 @@ private class Geary.Imap.FolderSession : Geary.Imap.SessionObject {
             if (msg_flags_add.size > 0) {
                 cmds.add(
                     new StoreCommand(
-                        msg_set, msg_flags_add, ADD_FLAGS, cancellable
+                        msg_set,
+                        ADD_FLAGS,
+                        SILENT,
+                        msg_flags_add,
+                        cancellable
                     )
                 );
             }
@@ -706,7 +710,11 @@ private class Geary.Imap.FolderSession : Geary.Imap.SessionObject {
             if (msg_flags_remove.size > 0) {
                 cmds.add(
                     new StoreCommand(
-                        msg_set, msg_flags_remove, REMOVE_FLAGS, cancellable
+                        msg_set,
+                        REMOVE_FLAGS,
+                        SILENT,
+                        msg_flags_remove,
+                        cancellable
                     )
                 );
             }
diff --git a/src/engine/imap/command/imap-store-command.vala b/src/engine/imap/command/imap-store-command.vala
index 4fbd614a..3250d737 100644
--- a/src/engine/imap/command/imap-store-command.vala
+++ b/src/engine/imap/command/imap-store-command.vala
@@ -6,6 +6,8 @@
  */
 
 /**
+ * The IMAP `STORE` and `UID STORE` commands.
+ *
  * See [[http://tools.ietf.org/html/rfc3501#section-6.4.6]]
  *
  * @see FetchCommand
@@ -13,37 +15,62 @@
  */
 public class Geary.Imap.StoreCommand : Command {
 
-    public const string NAME = "store";
-    public const string UID_NAME = "uid store";
+    public const string NAME = "STORE";
+    public const string UID_NAME = "UID STORE";
 
-    /**
-     * Options indicating functionality of the {@link StoreCommand}.
-     *
-     * Note that {@link ADD_FLAGS} and {@link REMOVE_FLAGS} are mutally exclusive.  REMOVE_FLAGS
-     * actually does not set a bit, meaning that removing is the default operation and, if both
-     * add and remove are set, an add occurs.
-     */
-    [Flags]
-    public enum Option {
-        REMOVE_FLAGS = 0,
+    /** Defines how the given flags are used to update message's flags. */
+    public enum Mode {
+
+        /** Sets the given flags as the complete set for the message's. */
+        SET_FLAGS,
+
+        /** Adds the given flags to the message's existing flags. */
         ADD_FLAGS,
+
+        /** Removes the given flags from the message's existing flags. */
+        REMOVE_FLAGS,
+    }
+
+    /** Specifies optional functionality for the command. */
+    [Flags]
+    public enum Options {
+
+        /** No options should be used. */
+        NONE,
+
+        /** Prevent the server from sending an untagged FETCH in response. */
         SILENT
     }
 
     public StoreCommand(MessageSet message_set,
+                        Mode mode,
+                        Options options,
                         Gee.List<MessageFlag> flag_list,
-                        Option options,
                         GLib.Cancellable? should_send) {
         base(message_set.is_uid ? UID_NAME : NAME, null, should_send);
 
-        bool add_flag = (options & Option.ADD_FLAGS) != 0;
-        bool silent = (options & Option.SILENT) != 0;
-
         this.args.add(message_set.to_parameter());
-        this.args.add(new AtomParameter("%sflags%s".printf(add_flag ? "+" : "-", silent ? ".silent" : "")));
 
-        ListParameter list = new ListParameter();
-        foreach(MessageFlag flag in flag_list) {
+        var command = new GLib.StringBuilder();
+        switch (mode) {
+        case ADD_FLAGS:
+            command.append_c('+');
+            break;
+        case REMOVE_FLAGS:
+            command.append_c('-');
+            break;
+        case SET_FLAGS:
+            // noop
+            break;
+        }
+        command.append("FLAGS");
+        if (Options.SILENT in options) {
+            command.append(".SILENT");
+        }
+        this.args.add(new AtomParameter(command.str));
+
+        var list = new ListParameter();
+        foreach (var flag in flag_list) {
             list.add(new AtomParameter(flag.value));
         }