diff --git a/cpp/src/slice2py/PythonUtil.cpp b/cpp/src/slice2py/PythonUtil.cpp
index 44ddd8ecbb5..da34feed6d3 100644
--- a/cpp/src/slice2py/PythonUtil.cpp
+++ b/cpp/src/slice2py/PythonUtil.cpp
@@ -230,6 +230,21 @@ lookupKwd(const string& name)
     return found ? "_" + name : name;
 }
 
+static string
+getDictLookup(const ContainedPtr& cont, const string& suffix = "", const string& prefix = "")
+{
+    string scope = Slice::Python::scopedToName(cont->scope());
+    assert(!scope.empty());
+
+    string package = Slice::Python::getPackageMetadata(cont);
+    if (!package.empty())
+    {
+        scope = package + "." + scope;
+    }
+
+    return "'" + suffix + Slice::Python::fixIdent(cont->name() + prefix) + "' not in _M_" + scope + "__dict__";
+}
+
 //
 // ModuleVisitor implementation.
 //
@@ -362,8 +377,11 @@ Slice::Python::CodeVisitor::visitClassDecl(const ClassDeclPtr& p)
     string scoped = p->scoped();
     if (_classHistory.count(scoped) == 0)
     {
+        _out << sp << nl << "if " << getDictLookup(p) << ':';
+        _out.inc();
         _out << nl << "_M_" << getAbsolute(p, "_t_") << " = IcePy.declareValue('" << scoped << "')";
         _classHistory.insert(scoped); // Avoid redundant declarations.
+        _out.dec();
     }
 }
 
@@ -376,9 +394,12 @@ Slice::Python::CodeVisitor::visitInterfaceDecl(const InterfaceDeclPtr& p)
     string scoped = p->scoped();
     if (_classHistory.count(scoped) == 0)
     {
+        _out << sp << nl << "if " << getDictLookup(p) << ':';
+        _out.inc();
         _out << nl << "_M_" << getAbsolute(p, "_t_", "Disp") << " = IcePy.declareClass('" << scoped << "')";
         _out << nl << "_M_" << getAbsolute(p, "_t_", "Prx") << " = IcePy.declareProxy('" << scoped << "')";
         _classHistory.insert(scoped); // Avoid redundant declarations.
+        _out.dec();
     }
 }
 
@@ -450,6 +471,9 @@ Slice::Python::CodeVisitor::visitClassDefStart(const ClassDefPtr& p)
     string valueName = fixIdent(p->name());
     ClassDefPtr base = p->base();
 
+    _out << sp << nl << "if " << getDictLookup(p) << ':';
+    _out.inc();
+
     _out << nl << "_M_" << abs << " = None";
     _out << nl << "class " << valueName << '(';
     if (!base)
@@ -602,6 +626,7 @@ Slice::Python::CodeVisitor::visitClassDefStart(const ClassDefPtr& p)
     {
         _classHistory.insert(scoped); // Avoid redundant declarations.
     }
+    _out.dec();
 
     return false;
 }
@@ -620,6 +645,9 @@ Slice::Python::CodeVisitor::visitInterfaceDefStart(const InterfaceDefPtr& p)
     string prxType = getAbsolute(p, "_t_", "Prx");
     InterfaceList bases = p->bases();
 
+    _out << sp << nl << "if " << getDictLookup(p) << ':';
+    _out.inc();
+
     // TODO: remove this interface-by-value.
     _out << sp << nl << "_M_" << type << " = IcePy.defineValue('" << scoped << "', Ice.Value, -1, ";
     writeMetaData(p->getMetaData());
@@ -1002,6 +1030,7 @@ Slice::Python::CodeVisitor::visitInterfaceDefStart(const InterfaceDefPtr& p)
     {
         _classHistory.insert(scoped); // Avoid redundant declarations.
     }
+    _out.dec();
 
     return false;
 }
@@ -1013,6 +1042,9 @@ Slice::Python::CodeVisitor::visitExceptionStart(const ExceptionPtr& p)
     string abs = getAbsolute(p);
     string name = fixIdent(p->name());
 
+    _out << sp << nl << "if " << getDictLookup(p) << ':';
+    _out.inc();
+
     _out << nl << "_M_" << abs << " = None";
     _out << nl << "class " << name << '(';
     ExceptionPtr base = p->base();
@@ -1141,6 +1173,8 @@ Slice::Python::CodeVisitor::visitExceptionStart(const ExceptionPtr& p)
 
     registerName(name);
 
+    _out.dec();
+
     return false;
 }
 
@@ -1163,6 +1197,9 @@ Slice::Python::CodeVisitor::visitStructStart(const StructPtr& p)
         }
     }
 
+    _out << sp << nl << "if " << getDictLookup(p) << ':';
+    _out.inc();
+
     _out << nl << "_M_" << abs << " = None";
     _out << nl << "class " << name << "(object):";
     _out.inc();
@@ -1410,25 +1447,36 @@ Slice::Python::CodeVisitor::visitStructStart(const StructPtr& p)
 
     registerName(name);
 
+    _out.dec();
+
     return false;
 }
 
 void
 Slice::Python::CodeVisitor::visitSequence(const SequencePtr& p)
 {
+    _out << sp << nl << "if " << getDictLookup(p) << ':';
+    _out.inc();
+
     // Emit the type information.
     StringList metaData = p->getMetaData();
     string scoped = p->scoped();
+
     _out << nl << "_M_" << getAbsolute(p, "_t_") << " = IcePy.defineSequence('" << scoped << "', ";
     writeMetaData(metaData);
     _out << ", ";
     writeType(p->type());
     _out << ")";
+
+    _out.dec();
 }
 
 void
 Slice::Python::CodeVisitor::visitDictionary(const DictionaryPtr& p)
 {
+    _out << sp << nl << "if " << getDictLookup(p) << ':';
+    _out.inc();
+
     // Emit the type information.
     string scoped = p->scoped();
     _out << nl << "_M_" << getAbsolute(p, "_t_") << " = IcePy.defineDictionary('" << scoped << "', ";
@@ -1438,11 +1486,16 @@ Slice::Python::CodeVisitor::visitDictionary(const DictionaryPtr& p)
     _out << ", ";
     writeType(p->valueType());
     _out << ")";
+
+    _out.dec();
 }
 
 void
 Slice::Python::CodeVisitor::visitEnum(const EnumPtr& p)
 {
+    _out << sp << nl << "if " << getDictLookup(p) << ':';
+    _out.inc();
+
     string scoped = p->scoped();
     string abs = getAbsolute(p);
     string name = fixIdent(p->name());
@@ -1499,16 +1552,23 @@ Slice::Python::CodeVisitor::visitEnum(const EnumPtr& p)
     _out << ", " << name << "._enumerators)";
 
     registerName(name);
+
+    _out.dec();
 }
 
 void
 Slice::Python::CodeVisitor::visitConst(const ConstPtr& p)
 {
+    _out << sp << nl << "if " << getDictLookup(p) << ':';
+    _out.inc();
+
     Slice::TypePtr type = p->type();
     string name = fixIdent(p->name());
 
     _out << sp << nl << "_M_" << getAbsolute(p) << " = ";
     writeConstantValue(type, p->valueType(), p->value());
+
+    _out.dec();
 }
 
 string