diff --git a/bin/nyc.js b/bin/nyc.js
index 8f62054a3..5428c4e61 100755
--- a/bin/nyc.js
+++ b/bin/nyc.js
@@ -38,8 +38,7 @@ if (argv._[0] === 'report') {
   else config.instrumenter = './lib/instrumenters/istanbul'
 
   var nyc = (new NYC(config))
-  nyc.reset()
-
+  if (config.clean) nyc.reset()
   if (config.all) nyc.addAllFiles()
 
   var env = {
diff --git a/lib/config-util.js b/lib/config-util.js
index 5bdc177cf..dd7bb085a 100644
--- a/lib/config-util.js
+++ b/lib/config-util.js
@@ -219,6 +219,17 @@ Config.buildYargs = function (cwd) {
       type: 'boolean',
       global: false
     })
+    .option('clean', {
+      describe: 'should the .nyc_output folder be deleted before executing tests',
+      default: true,
+      type: 'boolean',
+      global: false
+    })
+    .option('temp-directory', {
+      describe: 'directory to output raw coverage data in',
+      default: './.nyc_output',
+      global: false
+    })
     .pkgConf('nyc', cwd || process.cwd())
     .example('$0 npm test', 'instrument your tests with coverage')
     .example('$0 --require babel-core/register npm test', 'instrument your tests with coverage and babel')
diff --git a/package.json b/package.json
index 533dc1b1a..63563b0dd 100644
--- a/package.json
+++ b/package.json
@@ -11,7 +11,7 @@
     "build": "node ./build-tests",
     "instrument": "node ./build-self-coverage.js",
     "test-integration": "tap -t120 --no-cov -b ./test/build/*.js && mocha --timeout=15000 ./test/src/nyc-bin.js",
-    "test-mocha": "./bin/nyc.js --silent --temp-directory=./.self_coverage mocha ./test/nyc.js ./test/process-args.js",
+    "test-mocha": "./bin/nyc.js --no-clean --silent --temp-directory=./.self_coverage mocha ./test/nyc.js ./test/process-args.js",
     "report": "node ./bin/nyc  --temp-directory ./.self_coverage/ -r text -r lcov report",
     "release": "standard-version"
   },