diff --git a/lib/database.cc b/lib/database.cc
index a47a71d5..4e687060 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -390,8 +390,8 @@ find_document_for_doc_id (notmuch_database_t *notmuch, unsigned doc_id)
  *
  *	notmuch-sha1-<sha1_sum_of_message_id>
  */
-static char *
-_message_id_compressed (void *ctx, const char *message_id)
+char *
+_notmuch_message_id_compressed (void *ctx, const char *message_id)
 {
     char *sha1, *compressed;
 
@@ -415,7 +415,7 @@ notmuch_database_find_message (notmuch_database_t *notmuch,
 	return NOTMUCH_STATUS_NULL_POINTER;
 
     if (strlen (message_id) > NOTMUCH_MESSAGE_ID_MAX)
-	message_id = _message_id_compressed (notmuch, message_id);
+	message_id = _notmuch_message_id_compressed (notmuch, message_id);
 
     try {
 	status = _notmuch_database_find_unique_doc_id (notmuch, "id",
@@ -1728,7 +1728,7 @@ static char *
 _get_metadata_thread_id_key (void *ctx, const char *message_id)
 {
     if (strlen (message_id) > NOTMUCH_MESSAGE_ID_MAX)
-	message_id = _message_id_compressed (ctx, message_id);
+	message_id = _notmuch_message_id_compressed (ctx, message_id);
 
     return talloc_asprintf (ctx, NOTMUCH_METADATA_THREAD_ID_PREFIX "%s",
 			    message_id);
@@ -2100,14 +2100,6 @@ notmuch_database_add_message (notmuch_database_t *notmuch,
 	     * better than no message-id at all. */
 	    if (message_id == NULL)
 		message_id = talloc_strdup (message_file, header);
-
-	    /* If a message ID is too long, substitute its sha1 instead. */
-	    if (message_id && strlen (message_id) > NOTMUCH_MESSAGE_ID_MAX) {
-		char *compressed = _message_id_compressed (message_file,
-							   message_id);
-		talloc_free (message_id);
-		message_id = compressed;
-	    }
 	}
 
 	if (message_id == NULL ) {
diff --git a/lib/message.cc b/lib/message.cc
index 7e825480..bbfc2500 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -226,6 +226,10 @@ _notmuch_message_create_for_message_id (notmuch_database_t *notmuch,
     else if (*status_ret)
 	return NULL;
 
+    /* If the message ID is too long, substitute its sha1 instead. */
+    if (strlen (message_id) > NOTMUCH_MESSAGE_ID_MAX)
+	message_id = _notmuch_message_id_compressed (message, message_id);
+
     term = talloc_asprintf (NULL, "%s%s",
 			    _find_prefix ("id"), message_id);
     if (term == NULL) {
diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
index 17f30613..36cc12b0 100644
--- a/lib/notmuch-private.h
+++ b/lib/notmuch-private.h
@@ -174,6 +174,9 @@ typedef struct _notmuch_doc_id_set notmuch_doc_id_set_t;
 const char *
 _find_prefix (const char *name);
 
+char *
+_notmuch_message_id_compressed (void *ctx, const char *message_id);
+
 notmuch_status_t
 _notmuch_database_ensure_writable (notmuch_database_t *notmuch);