diff --git a/examples/custom_schema.cpp b/examples/custom_schema.cpp
index 555601a..e69a41a 100644
--- a/examples/custom_schema.cpp
+++ b/examples/custom_schema.cpp
@@ -158,11 +158,11 @@ void addRequiredConstraint(Schema &schema)
 {
     // Add a RequiredConstraint to the schema, specifying that the category,
     // price, and title properties must be present.
-    RequiredConstraint::RequiredProperties requiredProperties;
-    requiredProperties.insert("category");
-    requiredProperties.insert("price");
-    requiredProperties.insert("title");
-    schema.addConstraint(RequiredConstraint(requiredProperties));
+    RequiredConstraint constraint;
+    constraint.addRequiredProperty("category");
+    constraint.addRequiredProperty("price");
+    constraint.addRequiredProperty("title");
+    schema.addConstraint(constraint);
 }
 
 void addTypeConstraint(Schema &schema)
diff --git a/include/valijson/constraints/concrete_constraints.hpp b/include/valijson/constraints/concrete_constraints.hpp
index 82cdc20..ddbf1a6 100644
--- a/include/valijson/constraints/concrete_constraints.hpp
+++ b/include/valijson/constraints/concrete_constraints.hpp
@@ -552,17 +552,44 @@ struct PropertiesConstraint: BasicConstraint<PropertiesConstraint> {
 /**
  * @brief   Represents a 'required' constraint.
  */
-struct RequiredConstraint: BasicConstraint<RequiredConstraint>
+class RequiredConstraint: public BasicConstraint<RequiredConstraint>
 {
-    typedef std::set<std::string> RequiredProperties;
+public:
+    RequiredConstraint()
+      : requiredProperties(std::less<String>(), allocator) { }
 
-    RequiredConstraint(const RequiredProperties &requiredProperties)
-      : requiredProperties(requiredProperties)
+    RequiredConstraint(CustomAlloc allocFn, CustomFree freeFn)
+      : BasicConstraint(allocFn, freeFn),
+        requiredProperties(std::less<String>(), allocator) { }
+
+    bool addRequiredProperty(const char *propertyName)
     {
-
+        return requiredProperties.insert(String(propertyName,
+                Allocator::rebind<char>::other(allocator))).second;
     }
 
-    const RequiredProperties requiredProperties;
+    template<typename AllocatorType>
+    bool addRequiredProperty(const std::basic_string<char,
+            std::char_traits<char>, AllocatorType> &propertyName)
+    {
+        return addRequiredProperty(propertyName.c_str());
+    }
+
+    template<typename FunctorType>
+    void applyToRequiredProperties(const FunctorType &fn) const
+    {
+        BOOST_FOREACH( const String &propertyName, requiredProperties ) {
+            if (!fn(propertyName)) {
+                return;
+            }
+        }
+    }
+
+private:
+    typedef std::set<String, std::less<String>,
+            internal::CustomAllocator<String> > RequiredProperties;
+
+    RequiredProperties requiredProperties;
 };
 
 /**
diff --git a/include/valijson/constraints/constraint_visitor.hpp b/include/valijson/constraints/constraint_visitor.hpp
index ced9dec..ac8587e 100644
--- a/include/valijson/constraints/constraint_visitor.hpp
+++ b/include/valijson/constraints/constraint_visitor.hpp
@@ -19,13 +19,14 @@ struct MultipleOfConstraint;
 struct NotConstraint;
 struct PatternConstraint;
 struct PropertiesConstraint;
-struct RequiredConstraint;
+
 
 class AllOfConstraint;
 class AnyOfConstraint;
 class DependenciesConstraint;
 class LinearItemsConstraint;
 class OneOfConstraint;
+class RequiredConstraint;
 class SingularItemsConstraint;
 class TypeConstraint;
 class UniqueItemsConstraint;
diff --git a/include/valijson/schema_parser.hpp b/include/valijson/schema_parser.hpp
index 9c01697..d1a7fc4 100644
--- a/include/valijson/schema_parser.hpp
+++ b/include/valijson/schema_parser.hpp
@@ -1372,9 +1372,9 @@ private:
         }
 
         if (node.asBool()) {
-            constraints::RequiredConstraint::RequiredProperties requiredProperties;
-            requiredProperties.insert(name);
-            return constraints::RequiredConstraint(requiredProperties);
+            constraints::RequiredConstraint constraint;
+            constraint.addRequiredProperty(name);
+            return constraint;
         }
 
         return boost::none;
@@ -1395,15 +1395,18 @@ private:
     constraints::RequiredConstraint makeRequiredConstraint(
         const AdapterType &node)
     {
-        constraints::RequiredConstraint::RequiredProperties requiredProperties;
+        constraints::RequiredConstraint constraint;
+
         BOOST_FOREACH( const AdapterType v, node.getArray() ) {
             if (!v.isString()) {
-                // @todo throw exception
+                throw std::runtime_error("Expected required property name to "
+                        "be a string value");
             }
-            requiredProperties.insert(v.getString());
+
+            constraint.addRequiredProperty(v.getString());
         }
 
-        return constraints::RequiredConstraint(requiredProperties);
+        return constraint;
     }
 
     /**
diff --git a/include/valijson/validation_visitor.hpp b/include/valijson/validation_visitor.hpp
index 9337f5e..af07329 100644
--- a/include/valijson/validation_visitor.hpp
+++ b/include/valijson/validation_visitor.hpp
@@ -887,23 +887,16 @@ public:
     {
         if ((strictTypes && !target.isObject()) || !target.maybeObject()) {
             if (results) {
-                results->pushError(context, "Object required to validate 'required' properties.");
+                results->pushError(context,
+                        "Object required to validate 'required' properties.");
             }
             return false;
         }
 
         bool validated = true;
         const typename AdapterType::Object object = target.asObject();
-        BOOST_FOREACH( const std::string &requiredProperty, constraint.requiredProperties ) {
-            if (object.find(requiredProperty) == object.end()) {
-                if (results) {
-                    results->pushError(context, "Missing required property '" + requiredProperty + "'.");
-                    validated = false;
-                } else {
-                    return false;
-                }
-            }
-        }
+        constraint.applyToRequiredProperties(ValidateProperties(object, context,
+                true, results != NULL, results, &validated));
 
         return validated;
     }
@@ -1053,6 +1046,53 @@ public:
 
 private:
 
+    /**
+     * @brief  Functor to validate the presence of a set of properties
+     */
+    struct ValidateProperties
+    {
+        ValidateProperties(
+                const typename AdapterType::Object &object,
+                const std::vector<std::string> &context,
+                bool continueOnSuccess,
+                bool continueOnFailure,
+                ValidationResults *results,
+                bool *validated)
+          : object(object),
+            context(context),
+            continueOnSuccess(continueOnSuccess),
+            continueOnFailure(continueOnFailure),
+            results(results),
+            validated(validated) { }
+
+        template<typename StringType>
+        bool operator()(const StringType &property) const
+        {
+            if (object.find(property.c_str()) == object.end()) {
+                if (validated) {
+                    *validated = false;
+                }
+
+                if (results) {
+                    results->pushError(context, "Missing required property '" +
+                            std::string(property.c_str()) + "'.");
+                }
+
+                return continueOnFailure;
+            }
+
+            return continueOnSuccess;
+        }
+
+    private:
+        const typename AdapterType::Object &object;
+        const std::vector<std::string> &context;
+        bool continueOnSuccess;
+        bool continueOnFailure;
+        ValidationResults * const results;
+        bool * const validated;
+    };
+
     /**
      * @brief  Functor to validate property-based dependencies
      */