diff --git a/include/cereal/archives/xml.hpp b/include/cereal/archives/xml.hpp
index 58f51c9c9..755b80ced 100644
--- a/include/cereal/archives/xml.hpp
+++ b/include/cereal/archives/xml.hpp
@@ -114,14 +114,14 @@ namespace cereal
               @param indent Whether to indent each line of XML
               @param outputType Whether to output the type of each serialized object as an attribute
               @param sizeAttributes Whether dynamically sized containers output the size=dynamic attribute */
-          explicit Options( int precision = std::numeric_limits<double>::max_digits10,
-                            bool indent = true,
-                            bool outputType = false,
-                            bool sizeAttributes = true ) :
-            itsPrecision( precision ),
-            itsIndent( indent ),
-            itsOutputType( outputType ),
-            itsSizeAttributes( sizeAttributes )
+          explicit Options( int precision_ = std::numeric_limits<double>::max_digits10,
+                            bool indent_ = true,
+                            bool outputType_ = false,
+                            bool sizeAttributes_ = true ) :
+            itsPrecision( precision_ ),
+            itsIndent( indent_ ),
+            itsOutputType( outputType_ ),
+            itsSizeAttributes( sizeAttributes_ )
           { }
 
           /*! @name Option Modifiers
@@ -136,6 +136,8 @@ namespace cereal
               */
           //! @{
 
+          //! Sets the precision used for floaing point numbers
+          Options & precision( int value ){ itsPrecision = value; return * this; }
           //! Whether to indent each line of XML
           Options & indent( bool enable ){ itsIndent = enable; return *this; }
           //! Whether to output the type of each serialized object as an attribute
diff --git a/include/cereal/details/polymorphic_impl.hpp b/include/cereal/details/polymorphic_impl.hpp
index 772f02fdb..32e2881f8 100644
--- a/include/cereal/details/polymorphic_impl.hpp
+++ b/include/cereal/details/polymorphic_impl.hpp
@@ -115,8 +115,10 @@ namespace cereal
         all registered mappings between base and derived types. */
     struct PolymorphicCasters
     {
+      //! Maps from a derived type index to a set of chainable casters
+      using DerivedCasterMap = std::unordered_map<std::type_index, std::vector<PolymorphicCaster const *>>;
       //! Maps from base type index to a map from derived type index to caster
-      std::unordered_map<std::type_index, std::unordered_map<std::type_index, std::vector<PolymorphicCaster const*>>> map;
+      std::unordered_map<std::type_index, DerivedCasterMap> map;
 
       std::multimap<std::type_index, std::type_index> reverseMap;
 
@@ -241,7 +243,7 @@ namespace cereal
         auto & baseMap = StaticObject<PolymorphicCasters>::getInstance().map;
 
         {
-          auto & derivedMap = baseMap.insert( {baseKey, {}} ).first->second;
+          auto & derivedMap = baseMap.insert( {baseKey, PolymorphicCasters::DerivedCasterMap{}} ).first->second;
           auto & derivedVec = derivedMap.insert( {derivedKey, {}} ).first->second;
           derivedVec.push_back( this );
         }