diff --git a/CHANGELOG.yaml b/CHANGELOG.yaml
index 60bdbf5..6817b09 100644
--- a/CHANGELOG.yaml
+++ b/CHANGELOG.yaml
@@ -1,3 +1,7 @@
+unreleased:
+  new features:
+    - GH-640 Added option to allow blocking globals in specific executions
+
 2.1.0:
   date: 2024-02-28
   new features:
diff --git a/README.md b/README.md
index 7dfead0..f9bd68c 100644
--- a/README.md
+++ b/README.md
@@ -53,8 +53,8 @@ An asynchronous script will require an explicit call of a global function `__exi
 ```javascript
 myscope.set('setTimeout', global.setTimeout); // inject setTimeout
 
-// note the 2nd parameter is set to `true` for async
-myscope.exec('setTimeout(function () { __exitscope(null); }, 1000)', true, function (err) {
+// note the 2nd parameter is set to `{ async: true }`
+myscope.exec('setTimeout(function () { __exitscope(null); }, 1000)', { async: true }, function (err) {
     err ? console.error(err.stack || err) : console.log('execution complete');
 });
 ```
diff --git a/lib/index.js b/lib/index.js
index 9b82857..9776ddc 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -162,17 +162,25 @@ class Uniscope {
      * Executes a string within a protected Uniscope of controlled set of globals.
      *
      * @param {String} code A string representing a JavaScript expression, statement, or sequence of statements
-     * @param {Boolean} [async=false] When set to true, callback will be called when `__exitscope` is triggered
+     * @param {Object} [options] An object of options for the exec
+     * @param {Boolean} [options.async=false] When set to true, callback will be called when `__exitscope` is triggered
+     * @param {String[]} [options.block] Specify a set of global variables that will not be allowed to trickle in
      * @param {Function} callback Callback function to be called at the end of execution
      */
-    exec (code, async, callback) {
+    exec (code, options, callback) {
         // allow polymorphic parameter to enable async functions
         // and validate the primary code parameter
-        if (async && !callback) {
-            callback = async;
-            async = false;
+        if (options && !callback) {
+            callback = options;
+            options = {};
         }
 
+        if (typeof options === 'boolean') {
+            options = { async: options };
+        }
+
+        const async = Boolean(options && options.async);
+
         if (!util.isFunction(callback)) { throw new Error(ERROR_CALLBACK_MISSING); }
         if (!util.isString(code)) { return callback(new TypeError(ERROR_CODE_MUST_BE_STRING)); }
 
@@ -233,7 +241,7 @@ class Uniscope {
         });
 
         // based on Uniscope configuration, the globals that we block are specifically set to undefined
-        util.forEach(blocked, (key) => {
+        util.forEach(blocked.concat(options.block || []), (key) => {
             let position = globals.indexOf(key);
 
             (position === -1) && (position = globals.length);
diff --git a/test/unit/scope-exec.test.js b/test/unit/scope-exec.test.js
index c063874..43b5dd9 100644
--- a/test/unit/scope-exec.test.js
+++ b/test/unit/scope-exec.test.js
@@ -100,4 +100,37 @@ describe('scope module exec', function () {
             expect(d).to.equal(4);
         `, done);
     });
+
+    it('should allow blocking globals in specific executions', function (done) {
+        scope.set('myGlobal', 'my_global');
+
+        scope.set('blockedExecution', function () {
+            scope.exec(`
+                expect(myGlobal).to.equal(undefined);
+                unblockedExecution(); // call execution from inside the blocked scope
+                try {
+                    Function('return myGlobal')();
+                    throw new Error('myGlobal is not blocked');
+                } catch (e) {
+                    expect(e).to.be.an('error');
+                    expect(e.message).to.equal('myGlobal is not defined');
+                }
+            `, { block: ['myGlobal'] }, function (err) {
+                expect(err, 'error in blockedExecution').to.be.undefined;
+            });
+        });
+
+        scope.set('unblockedExecution', function () {
+            scope.exec(`
+                expect(myGlobal).to.equal('my_global');
+            `, function (err) {
+                expect(err, 'error in unblockedExecution').to.be.undefined;
+            });
+        });
+
+        scope.exec(`
+            blockedExecution();
+            unblockedExecution();
+        `, done);
+    });
 });