diff --git a/wrap/ReturnType.cpp b/wrap/ReturnType.cpp
index a317a5420..25147e59a 100644
--- a/wrap/ReturnType.cpp
+++ b/wrap/ReturnType.cpp
@@ -26,7 +26,7 @@ void ReturnType::wrap_result(const string& out, const string& result,
   if (category == CLASS) {
     string objCopy, ptrType;
     ptrType = "Shared" + name;
-    const bool isVirtual = typeAttributes.at(cppType).isVirtual;
+    const bool isVirtual = typeAttributes.attributes(cppType).isVirtual;
     if (isVirtual) {
       if (isPtr)
         objCopy = result;
diff --git a/wrap/TypeAttributesTable.cpp b/wrap/TypeAttributesTable.cpp
index 16055fca1..14c1ab7a4 100644
--- a/wrap/TypeAttributesTable.cpp
+++ b/wrap/TypeAttributesTable.cpp
@@ -21,42 +21,61 @@
 #include "utilities.h"
 
 #include <boost/foreach.hpp>
+#include <boost/range/adaptor/map.hpp>
+#include <boost/range/algorithm/copy.hpp>
 
+#include <iterator>     // std::ostream_iterator
 using namespace std;
 
 namespace wrap {
 
-  /* ************************************************************************* */
-  void TypeAttributesTable::addClasses(const vector<Class>& classes) {
-    BOOST_FOREACH(const Class& cls, classes) {
-      if(!insert(make_pair(cls.qualifiedName("::"), TypeAttributes(cls.isVirtual))).second)
-        throw DuplicateDefinition("class " + cls.qualifiedName("::"));
-    }
+/* ************************************************************************* */
+const TypeAttributes& TypeAttributesTable::attributes(const string& key) const {
+  try {
+    return table_.at(key);
+  } catch (const out_of_range& oor) {
+    cerr << "Class::method: key not found: " << oor.what()
+        << ", methods are:\n";
+    using boost::adaptors::map_keys;
+    ostream_iterator<string> out_it(cerr, "\n");
+    boost::copy(table_ | map_keys, out_it);
+    throw runtime_error("Internal error in wrap");
   }
+}
 
-  /* ************************************************************************* */
-  void TypeAttributesTable::addForwardDeclarations(const vector<ForwardDeclaration>& forwardDecls) {
-    BOOST_FOREACH(const ForwardDeclaration& fwDec, forwardDecls) {
-      if(!insert(make_pair(fwDec.name, TypeAttributes(fwDec.isVirtual))).second)
-        throw DuplicateDefinition("class " + fwDec.name);
-    }
+/* ************************************************************************* */
+void TypeAttributesTable::addClasses(const vector<Class>& classes) {
+  BOOST_FOREACH(const Class& cls, classes) {
+    if (!table_.insert(
+        make_pair(cls.qualifiedName("::"), TypeAttributes(cls.isVirtual))).second)
+      throw DuplicateDefinition("class " + cls.qualifiedName("::"));
   }
+}
 
-  /* ************************************************************************* */
-  void TypeAttributesTable::checkValidity(const vector<Class>& classes) const {
-    BOOST_FOREACH(const Class& cls, classes) {
-      // Check that class is virtual if it has a parent
-      if (!cls.qualifiedParent.empty() && !cls.isVirtual)
-        throw AttributeError(cls.qualifiedName("::"),
-            "Has a base class so needs to be declared virtual, change to 'virtual class "
-                + cls.name + " ...'");
-      // Check that parent is virtual as well
-      Qualified parent = cls.qualifiedParent;
-      if (!parent.empty() && !at(parent.qualifiedName("::")).isVirtual)
-        throw AttributeError(parent.qualifiedName("::"),
-            "Is the base class of " + cls.qualifiedName("::")
-                + ", so needs to be declared virtual");
-    }
+/* ************************************************************************* */
+void TypeAttributesTable::addForwardDeclarations(
+    const vector<ForwardDeclaration>& forwardDecls) {
+  BOOST_FOREACH(const ForwardDeclaration& fwDec, forwardDecls) {
+    if (!table_.insert(make_pair(fwDec.name, TypeAttributes(fwDec.isVirtual))).second)
+      throw DuplicateDefinition("class " + fwDec.name);
   }
+}
+
+/* ************************************************************************* */
+void TypeAttributesTable::checkValidity(const vector<Class>& classes) const {
+  BOOST_FOREACH(const Class& cls, classes) {
+    // Check that class is virtual if it has a parent
+    if (!cls.qualifiedParent.empty() && !cls.isVirtual)
+      throw AttributeError(cls.qualifiedName("::"),
+          "Has a base class so needs to be declared virtual, change to 'virtual class "
+              + cls.name + " ...'");
+    // Check that parent is virtual as well
+    Qualified parent = cls.qualifiedParent;
+    if (!parent.empty() && !table_.at(parent.qualifiedName("::")).isVirtual)
+      throw AttributeError(parent.qualifiedName("::"),
+          "Is the base class of " + cls.qualifiedName("::")
+              + ", so needs to be declared virtual");
+  }
+}
 
 }
diff --git a/wrap/TypeAttributesTable.h b/wrap/TypeAttributesTable.h
index d2a346bfc..9b1c2acbc 100644
--- a/wrap/TypeAttributesTable.h
+++ b/wrap/TypeAttributesTable.h
@@ -27,9 +27,9 @@
 
 namespace wrap {
 
-  // Forward declarations
-  class Class;
-  
+// Forward declarations
+class Class;
+
 /** Attributes about valid classes, both for classes defined in this module and
  * also those forward-declared from others.  At the moment this only contains
  * whether the class is virtual, which is used to know how to copy the class,
@@ -37,18 +37,33 @@ namespace wrap {
  */
 struct TypeAttributes {
   bool isVirtual;
-  TypeAttributes() : isVirtual(false) {}
-  TypeAttributes(bool isVirtual) : isVirtual(isVirtual) {}
+  TypeAttributes() :
+      isVirtual(false) {
+  }
+  TypeAttributes(bool isVirtual) :
+      isVirtual(isVirtual) {
+  }
 };
 
 /** Map of type names to attributes. */
-class TypeAttributesTable : public std::map<std::string, TypeAttributes> {
+class TypeAttributesTable {
+
+  std::map<std::string, TypeAttributes> table_;
+
 public:
-  TypeAttributesTable() {}
+
+  /// Constructor
+  TypeAttributesTable() {
+  }
 
   void addClasses(const std::vector<Class>& classes);
-  void addForwardDeclarations(const std::vector<ForwardDeclaration>& forwardDecls);
+  void addForwardDeclarations(
+      const std::vector<ForwardDeclaration>& forwardDecls);
 
+  /// Access attributes associated with key, informative failure
+  const TypeAttributes& attributes(const std::string& key) const;
+
+  /// Check that all virtual classes are properly defined
   void checkValidity(const std::vector<Class>& classes) const;
 };