diff --git a/chrome/content/zotero/xpcom/utilities_internal.js b/chrome/content/zotero/xpcom/utilities_internal.js
index 686a30aeab..142d06b13f 100644
--- a/chrome/content/zotero/xpcom/utilities_internal.js
+++ b/chrome/content/zotero/xpcom/utilities_internal.js
@@ -165,9 +165,9 @@ Zotero.Utilities.Internal = {
 			.createInstance(Components.interfaces.nsICryptoHash);
 		ch.init(ch.MD5);
 		
+		var is = Cc["@mozilla.org/network/file-input-stream;1"]
+			.createInstance(Ci.nsIFileInputStream);
 		try {
-			let is = Cc["@mozilla.org/network/file-input-stream;1"]
-				.createInstance(Ci.nsIFileInputStream);
 			is.init(Zotero.File.pathToFile(file), -1, -1, Ci.nsIFileInputStream.CLOSE_ON_EOF);
 			ch.updateFromStream(is, -1);
 			// Get binary string and convert to hex string
@@ -187,6 +187,9 @@ Zotero.Utilities.Internal = {
 			}
 			throw e;
 		}
+		finally {
+			is.close();
+		}
 	},