diff --git a/chrome/content/zotero/preferences/preferences.js b/chrome/content/zotero/preferences/preferences.js
index c3722121b3..13b7fcaf8e 100644
--- a/chrome/content/zotero/preferences/preferences.js
+++ b/chrome/content/zotero/preferences/preferences.js
@@ -1189,7 +1189,13 @@ function downloadPDFTool(tool, version, callback) {
 	
 	wbp.progressListener = progressListener;
 	Zotero.debug("Saving " + uri.spec + " to " + fileURL.spec);
-	wbp.saveURI(uri, null, null, null, null, fileURL);
+	try {
+		wbp.saveURI(uri, null, null, null, null, fileURL);
+	} catch(e if e.name === "NS_ERROR_XPC_NOT_ENOUGH_ARGS") {
+		// https://bugzilla.mozilla.org/show_bug.cgi?id=794602
+		// XXX Always use when we no longer support Firefox < 18
+		wbp.saveURI(uri, null, null, null, null, fileURL, null);
+	}
 }
 
 
diff --git a/chrome/content/zotero/xpcom/storage/webdav.js b/chrome/content/zotero/xpcom/storage/webdav.js
index 4e1d1b8bd3..531698c8c4 100644
--- a/chrome/content/zotero/xpcom/storage/webdav.js
+++ b/chrome/content/zotero/xpcom/storage/webdav.js
@@ -463,7 +463,13 @@ Zotero.Sync.Storage.Session.WebDAV.prototype.downloadFile = function (request) {
 				.createInstance(nsIWBP);
 			wbp.persistFlags = nsIWBP.PERSIST_FLAGS_BYPASS_CACHE;
 			wbp.progressListener = listener;
-			wbp.saveURI(uri, null, null, null, null, destFile);
+			try {
+				wbp.saveURI(uri, null, null, null, null, destFile);
+			} catch(e if e.name === "NS_ERROR_XPC_NOT_ENOUGH_ARGS") {
+				// https://bugzilla.mozilla.org/show_bug.cgi?id=794602
+				// XXX Always use when we no longer support Firefox < 18
+				wbp.saveURI(uri, null, null, null, null, destFile, null);
+			}
 		}
 		catch (e) {
 			request.error(e);
diff --git a/chrome/content/zotero/xpcom/storage/zfs.js b/chrome/content/zotero/xpcom/storage/zfs.js
index 1a72d6dd14..b4f7c657c9 100644
--- a/chrome/content/zotero/xpcom/storage/zfs.js
+++ b/chrome/content/zotero/xpcom/storage/zfs.js
@@ -315,8 +315,14 @@ Zotero.Sync.Storage.Session.ZFS.prototype.downloadFile = function (request) {
 				.classes["@mozilla.org/embedding/browser/nsWebBrowserPersist;1"]
 				.createInstance(nsIWBP);
 			wbp.persistFlags = nsIWBP.PERSIST_FLAGS_BYPASS_CACHE;
-			wbp.progressListener = listener;
-			wbp.saveURI(uri, null, null, null, null, destFile);
+			wbp.progressListener = listener;	
+			try {
+				wbp.saveURI(uri, null, null, null, null, destFile);
+			} catch(e if e.name === "NS_ERROR_XPC_NOT_ENOUGH_ARGS") {
+				// https://bugzilla.mozilla.org/show_bug.cgi?id=794602
+				// XXX Always use when we no longer support Firefox < 18
+				wbp.saveURI(uri, null, null, null, null, destFile, null);
+			}
 		}
 		catch (e) {
 			self.onError(e);