diff --git a/lib/repository.js b/lib/repository.js
index 121543ebd..1da4e29f5 100644
--- a/lib/repository.js
+++ b/lib/repository.js
@@ -1361,20 +1361,22 @@ Repository.prototype.stageLines =
 
   var repo = this;
   var index;
-  var diffPromise = isSelectionStaged ?
-    repo.getHeadCommit()
-      .then(function getTreeFromCommit(commit) {
-        return commit.getTree();
-      })
-      .then(function getDiffFromTree(tree) {
-        return NodeGit.Diff.treeToIndex(repo, tree, index);
-      })
-    :
-    NodeGit.Diff.indexToWorkdir(repo, index, {
-        flags:
-          NodeGit.Diff.OPTION.SHOW_UNTRACKED_CONTENT |
-          NodeGit.Diff.OPTION.RECURSE_UNTRACKED_DIRS
-      });
+  var diffPromise = function diffPromise() {
+    return isSelectionStaged ?
+      repo.getHeadCommit()
+        .then(function getTreeFromCommit(commit) {
+          return commit.getTree();
+        })
+        .then(function getDiffFromTree(tree) {
+          return NodeGit.Diff.treeToIndex(repo, tree, index);
+        })
+      :
+      NodeGit.Diff.indexToWorkdir(repo, index, {
+          flags:
+            NodeGit.Diff.OPTION.SHOW_UNTRACKED_CONTENT |
+            NodeGit.Diff.OPTION.RECURSE_UNTRACKED_DIRS
+        });
+    };
 
     //The following chain checks if there is a patch with no hunks left for the
     //file, and no filemode changes were done on the file. It is then safe to
@@ -1409,18 +1411,13 @@ Repository.prototype.stageLines =
       });
     };
 
-  var indexLock = repo.path().replace(".git/", "") + ".git/index.lock";
-
-  return fse.remove(indexLock)
-    .then(function() {
-      return repo.openIndex();
-    })
+  return repo.openIndex()
     .then(function(indexResult) {
       index = indexResult;
       return index.read(1);
     })
     .then(function() {
-      return diffPromise;
+      return diffPromise();
     })
     .then(function(diff) {
       if (!(NodeGit.Status.file(repo, filePath) &