diff --git a/src/com/fsck/k9/mail/store/ImapStore.java b/src/com/fsck/k9/mail/store/ImapStore.java
index 17441a600..cc3681706 100644
--- a/src/com/fsck/k9/mail/store/ImapStore.java
+++ b/src/com/fsck/k9/mail/store/ImapStore.java
@@ -1913,7 +1913,7 @@ public class ImapStore extends Store {
 
                 List<ImapResponse> responses =
                     executeSimpleCommand(
-                        String.format("UID SEARCH HEADER MESSAGE-ID %s", messageId));
+                        String.format("UID SEARCH HEADER MESSAGE-ID %s", encodeString(messageId)));
                 for (ImapResponse response1 : responses) {
                     if (response1.mTag == null && ImapResponseParser.equalsIgnoreCase(response1.get(0), "SEARCH")
                             && response1.size() > 1) {