diff --git a/.eslintrc b/.eslintrc
index 5e638d63..8e2f1479 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -1,5 +1,12 @@
 {
     "root": true,
+    "env": {
+        "browser": true,
+        "node": true,
+    },
+    "globals": {
+        "Promise": false,
+    },
     "rules": {
         "indent": ["error", 4],
         "key-spacing": "error",
@@ -8,6 +15,7 @@
             "anonymous": "always",
             "named": "never",
         }],
+        "no-undef": "error",
     },
     "overrides": [
         {
@@ -16,5 +24,11 @@
                 "ecmaVersion": 2017,
             },
         },
+        {
+            "files": ["example/**", "test/**"],
+            "globals": {
+                "g": false,
+            },
+        },
     ],
 }
diff --git a/test/promise_fail.js b/test/promise_fail.js
index f7148cc1..3fa8892a 100644
--- a/test/promise_fail.js
+++ b/test/promise_fail.js
@@ -17,7 +17,7 @@ tap.test('callback returning rejected promise should cause that test (and only t
             return tt.pass('the test file indicated it should be skipped');
         }
 
-        strippedString = stripFullStack(rowsString);
+        var strippedString = stripFullStack(rowsString);
 
         // hack for consistency across all versions of node
         // some versions produce a longer stack trace for some reason
@@ -60,7 +60,7 @@ tap.test('subtest callback returning rejected promise should cause that subtest
             return tt.pass('the test file indicated it should be skipped');
         }
 
-        strippedString = stripFullStack(rowsString);
+        var strippedString = stripFullStack(rowsString);
 
         // hack for consistency across all versions of node
         // some versions produce a longer stack trace for some reason
diff --git a/test/stackTrace.js b/test/stackTrace.js
index 681ce288..c5296600 100644
--- a/test/stackTrace.js
+++ b/test/stackTrace.js
@@ -107,7 +107,7 @@ tap.test('preserves stack trace for failed assertions', function (tt) {
     parser.once('assert', function (data) {
         tt.equal(typeof data.diag.at, 'string');
         tt.equal(typeof data.diag.stack, 'string');
-        at = data.diag.at || '';
+        var at = data.diag.at || '';
         stack = data.diag.stack || '';
         tt.ok(/^Error: true should be false(\n    at .+)+/.exec(stack), 'stack should be a stack');
         tt.deepEqual(data, {
@@ -172,7 +172,7 @@ tap.test('preserves stack trace for failed assertions where actual===falsy', fun
     parser.once('assert', function (data) {
         tt.equal(typeof data.diag.at, 'string');
         tt.equal(typeof data.diag.stack, 'string');
-        at = data.diag.at || '';
+        var at = data.diag.at || '';
         stack = data.diag.stack || '';
         tt.ok(/^Error: false should be true(\n    at .+)+/.exec(stack), 'stack should be a stack');
         tt.deepEqual(data, {