diff --git a/Source/cmState.cxx b/Source/cmState.cxx
index 53fdae0d6..4e4c2c6a1 100644
--- a/Source/cmState.cxx
+++ b/Source/cmState.cxx
@@ -1701,3 +1701,13 @@ std::vector<std::string> cmState::Directory::GetPropertyKeys() const
     }
   return keys;
 }
+
+bool operator==(const cmState::Snapshot& lhs, const cmState::Snapshot& rhs)
+{
+  return lhs.Position == rhs.Position;
+}
+
+bool operator!=(const cmState::Snapshot& lhs, const cmState::Snapshot& rhs)
+{
+  return lhs.Position != rhs.Position;
+}
diff --git a/Source/cmState.h b/Source/cmState.h
index e503cd258..d68306828 100644
--- a/Source/cmState.h
+++ b/Source/cmState.h
@@ -93,6 +93,10 @@ public:
     };
 
   private:
+    friend bool operator==(const cmState::Snapshot& lhs,
+                           const cmState::Snapshot& rhs);
+    friend bool operator!=(const cmState::Snapshot& lhs,
+                           const cmState::Snapshot& rhs);
     friend class cmState;
     friend class Directory;
     friend struct StrictWeakOrder;
@@ -314,4 +318,7 @@ private:
   bool MSYSShell;
 };
 
+bool operator==(const cmState::Snapshot& lhs, const cmState::Snapshot& rhs);
+bool operator!=(const cmState::Snapshot& lhs, const cmState::Snapshot& rhs);
+
 #endif