diff --git a/chrome/content/zotero/xpcom/attachments.js b/chrome/content/zotero/xpcom/attachments.js
index eff18de43..9889b72a0 100644
--- a/chrome/content/zotero/xpcom/attachments.js
+++ b/chrome/content/zotero/xpcom/attachments.js
@@ -24,6 +24,7 @@
 */
 
 Zotero.Attachments = new function(){
+	// Keep in sync with Zotero.Schema.integrityCheck()
 	this.LINK_MODE_IMPORTED_FILE = 0;
 	this.LINK_MODE_IMPORTED_URL = 1;
 	this.LINK_MODE_LINKED_FILE = 2;
diff --git a/chrome/content/zotero/xpcom/data/item.js b/chrome/content/zotero/xpcom/data/item.js
index 0bc14ddb9..3ecab174f 100644
--- a/chrome/content/zotero/xpcom/data/item.js
+++ b/chrome/content/zotero/xpcom/data/item.js
@@ -349,7 +349,10 @@ Zotero.Item.prototype._parseRowData = function(row) {
 				break;
 			
 			case 'attachmentLinkMode':
-				val = val !== null ? parseInt(val) : false;
+				val = val !== null
+					? parseInt(val)
+					// Shouldn't happen
+					: Zotero.Attachments.LINK_MODE_IMPORTED_URL;
 				break;
 			
 			case 'attachmentPath':
diff --git a/chrome/content/zotero/xpcom/schema.js b/chrome/content/zotero/xpcom/schema.js
index a833c26fc..8a61736be 100644
--- a/chrome/content/zotero/xpcom/schema.js
+++ b/chrome/content/zotero/xpcom/schema.js
@@ -1329,6 +1329,11 @@ Zotero.Schema = new function(){
 			[
 				"SELECT COUNT(*) > 1 FROM fulltextItems WHERE itemID NOT IN (SELECT itemID FROM items WHERE itemTypeID=14)",
 				"DELETE FROM fulltextItems WHERE itemID NOT IN (SELECT itemID FROM items WHERE itemTypeID=14)"
+			],
+			// Invalid link mode -- set to imported url
+			[
+				"SELECT COUNT(*) > 1 FROM itemAttachments WHERE linkMode NOT IN (0,1,2,3)",
+				"UPDATE itemAttachments SET linkMode=1 WHERE linkMode NOT IN (0,1,2,3)"
 			]
 		];