diff --git a/Source/cmPolicies.cxx b/Source/cmPolicies.cxx
index 899694309..f8d61db8d 100644
--- a/Source/cmPolicies.cxx
+++ b/Source/cmPolicies.cxx
@@ -343,24 +343,51 @@ cmPolicies::GetRequiredAlwaysPolicyError(cmPolicies::PolicyID id)
   return e.str();
 }
 
+cmPolicies::PolicyMap::PolicyMap()
+{
+  this->UNDEFINED.set();
+}
+
 cmPolicies::PolicyStatus
 cmPolicies::PolicyMap::Get(cmPolicies::PolicyID id) const
 {
-  return this->find(id)->second;
+  PolicyStatus status = cmPolicies::WARN;
+
+  if (this->OLD[id])
+    {
+    status = cmPolicies::OLD;
+    }
+  else if (this->NEW[id])
+    {
+    status = cmPolicies::NEW;
+    }
+  else if (this->REQUIRED_ALWAYS[id])
+    {
+    status = cmPolicies::REQUIRED_ALWAYS;
+    }
+  else if (this->REQUIRED_IF_USED[id])
+    {
+    status = cmPolicies::REQUIRED_IF_USED;
+    }
+  return status;
 }
 
 void cmPolicies::PolicyMap::Set(cmPolicies::PolicyID id,
                                 cmPolicies::PolicyStatus status)
 {
-  (*this)[id] = status;
+  this->UNDEFINED.reset(id);
+  this->OLD[id] = (status == cmPolicies::OLD);
+  this->NEW[id] = (status == cmPolicies::NEW);
+  this->REQUIRED_ALWAYS[id] = (status == cmPolicies::REQUIRED_ALWAYS);
+  this->REQUIRED_IF_USED[id] = (status == cmPolicies::REQUIRED_IF_USED);
 }
 
 bool cmPolicies::PolicyMap::IsDefined(cmPolicies::PolicyID id) const
 {
-  return this->find(id) != this->end();
+  return !this->UNDEFINED[id];
 }
 
 bool cmPolicies::PolicyMap::IsEmpty() const
 {
-  return this->empty();
+  return !this->UNDEFINED.none();
 }
diff --git a/Source/cmPolicies.h b/Source/cmPolicies.h
index 46b725ac5..63376dd7d 100644
--- a/Source/cmPolicies.h
+++ b/Source/cmPolicies.h
@@ -14,6 +14,8 @@
 
 #include "cmCustomCommand.h"
 
+#include <bitset>
+
 class cmMakefile;
 class cmPolicy;
 
@@ -268,12 +270,20 @@ public:
   static std::string GetRequiredAlwaysPolicyError(cmPolicies::PolicyID id);
 
   /** Represent a set of policy values.  */
-  struct PolicyMap : private std::map<PolicyID, PolicyStatus>
+  struct PolicyMap
   {
+    PolicyMap();
     PolicyStatus Get(PolicyID id) const;
     void Set(PolicyID id, PolicyStatus status);
     bool IsDefined(PolicyID id) const;
     bool IsEmpty() const;
+
+  private:
+    std::bitset<cmPolicies::CMPCOUNT> UNDEFINED;
+    std::bitset<cmPolicies::CMPCOUNT> OLD;
+    std::bitset<cmPolicies::CMPCOUNT> NEW;
+    std::bitset<cmPolicies::CMPCOUNT> REQUIRED_IF_USED;
+    std::bitset<cmPolicies::CMPCOUNT> REQUIRED_ALWAYS;
   };
 };