diff --git a/specs/validate-spec.js b/specs/validate-spec.js
index f18f6fc..da5606a 100644
--- a/specs/validate-spec.js
+++ b/specs/validate-spec.js
@@ -192,6 +192,27 @@ describe("validate", function() {
       ]);
     });
 
+    it("does not allow undeclared attributes in exclusive mode", function() {
+      var attributes = {name: "Nicklas", age: 23, year: 2018}
+        , globalOptions = {exclusive: true}
+        , constraints = {name: true};
+      expect(validate.runValidations(attributes, constraints, globalOptions)).toHaveItems([
+        {
+          attribute: "age",
+          value: 23,
+          globalOptions: globalOptions,
+          attributes: attributes,
+          error: "is not permitted (exclusive mode)"
+        }, {
+          attribute: "year",
+          value: 2018,
+          globalOptions: globalOptions,
+          attributes: attributes,
+          error: "is not permitted (exclusive mode)"
+        }
+      ]);
+    });
+
     it("allows the options for an attribute to be a function", function() {
       var options = {pass: {option1: "value1"}}
         , attrs = {name: "Nicklas"}
diff --git a/validate.js b/validate.js
index 610d0bc..f0141a9 100644
--- a/validate.js
+++ b/validate.js
@@ -80,6 +80,7 @@
     runValidations: function(attributes, constraints, options) {
       var results = []
         , attr
+        , constraint
         , validatorName
         , value
         , validators
@@ -91,6 +92,29 @@
         attributes = v.collectFormValues(attributes);
       }
 
+      // In 'exclusive' mode, make sure that there's a constraint for each and
+      // every attribute. Nested attribute names are matched as well.
+      if (options.exclusive === true) {
+        for (attr in attributes) {
+          value = v.getDeepObjectValue(attributes, attr);
+          var declared = false;
+          for (constraint in constraints) {
+            if (constraint === attr || constraint.indexOf(attr + ".") === 0) {
+              declared = true;
+            }
+          }
+          if (!declared) {
+            results.push({
+              attribute: attr,
+              value: value,
+              globalOptions: options,
+              attributes: attributes,
+              error: options.exclusiveErrorMessage || "is not permitted (exclusive mode)",
+            });
+          }
+        }
+      }
+
       // Loops through each constraints, finds the correct validator and run it.
       for (attr in constraints) {
         value = v.getDeepObjectValue(attributes, attr);