diff --git a/services/clsi/app/js/OutputFileFinder.js b/services/clsi/app/js/OutputFileFinder.js
index 1f62a7568d..38fdc7945e 100644
--- a/services/clsi/app/js/OutputFileFinder.js
+++ b/services/clsi/app/js/OutputFileFinder.js
@@ -2,6 +2,7 @@ let OutputFileFinder
 const async = require('async')
 const fs = require('fs')
 const Path = require('path')
+const _ = require('lodash')
 const { spawn } = require('child_process')
 const logger = require('logger-sharelatex')
 
@@ -32,7 +33,8 @@ module.exports = OutputFileFinder = {
     })
   },
 
-  _getAllFiles(directory, _callback) {
+  _getAllFiles(directory, callback) {
+    callback = _.once(callback)
     // don't include clsi-specific files/directories in the output list
     const EXCLUDE_DIRS = [
       '-name',
diff --git a/services/clsi/test/unit/js/OutputFileFinderTests.js b/services/clsi/test/unit/js/OutputFileFinderTests.js
index 4afa25e83e..8744c6e779 100644
--- a/services/clsi/test/unit/js/OutputFileFinderTests.js
+++ b/services/clsi/test/unit/js/OutputFileFinderTests.js
@@ -28,6 +28,9 @@ describe('OutputFileFinder', function () {
         fs: (this.fs = {}),
         child_process: { spawn: (this.spawn = sinon.stub()) },
         'logger-sharelatex': { log: sinon.stub(), warn: sinon.stub() }
+      },
+      globals: {
+        Math // used by lodash
       }
     })
     this.directory = '/test/dir'