diff --git a/include/yaml-cpp/exceptions.h b/include/yaml-cpp/exceptions.h
index f5dd1cf78..4a91249ab 100644
--- a/include/yaml-cpp/exceptions.h
+++ b/include/yaml-cpp/exceptions.h
@@ -90,6 +90,7 @@ const char* const INVALID_ALIAS = "invalid alias";
 const char* const INVALID_TAG = "invalid tag";
 const char* const BAD_FILE = "bad file";
 const char* const UNEXPECTED_TOKEN_AFTER_DOC = "unexpected token after end of document";
+const char* const NON_UNIQUE_MAP_KEY = "map keys must be unique";
 
 template <typename T>
 inline const std::string KEY_NOT_FOUND_WITH_KEY(
@@ -301,6 +302,16 @@ class YAML_CPP_API BadFile : public Exception {
   BadFile(const BadFile&) = default;
   ~BadFile() YAML_CPP_NOEXCEPT override;
 };
+
+class YAML_CPP_API NonUniqueMapKey : public RepresentationException {
+ public:
+  template <typename Key>
+  NonUniqueMapKey(const Mark& mark_, const Key& key)
+      : RepresentationException(mark_, ErrorMsg::NON_UNIQUE_MAP_KEY) {}
+  NonUniqueMapKey(const NonUniqueMapKey&) = default;
+  ~NonUniqueMapKey() YAML_CPP_NOEXCEPT override;
+};
+
 }  // namespace YAML
 
 #if defined(_MSC_VER)
diff --git a/include/yaml-cpp/node/detail/impl.h b/include/yaml-cpp/node/detail/impl.h
index b38038dfd..9138fe6b0 100644
--- a/include/yaml-cpp/node/detail/impl.h
+++ b/include/yaml-cpp/node/detail/impl.h
@@ -218,7 +218,7 @@ inline void node_data::force_insert(const Key& key, const Value& value,
 
   node& k = convert_to_node(key, pMemory);
   node& v = convert_to_node(value, pMemory);
-  insert_map_pair(k, v);
+  insert_map_pair(k, v, true);
 }
 
 template <typename T>
diff --git a/include/yaml-cpp/node/detail/node_data.h b/include/yaml-cpp/node/detail/node_data.h
index 07cf81aa0..ed7d9cdbf 100644
--- a/include/yaml-cpp/node/detail/node_data.h
+++ b/include/yaml-cpp/node/detail/node_data.h
@@ -90,7 +90,7 @@ class YAML_CPP_API node_data {
   void reset_sequence();
   void reset_map();
 
-  void insert_map_pair(node& key, node& value);
+  void insert_map_pair(node& key, node& value, bool force = false);
   void convert_to_map(const shared_memory_holder& pMemory);
   void convert_sequence_to_map(const shared_memory_holder& pMemory);
 
diff --git a/src/exceptions.cpp b/src/exceptions.cpp
index 43a7976e9..af99fd6b7 100644
--- a/src/exceptions.cpp
+++ b/src/exceptions.cpp
@@ -17,4 +17,5 @@ BadPushback::~BadPushback() YAML_CPP_NOEXCEPT = default;
 BadInsert::~BadInsert() YAML_CPP_NOEXCEPT = default;
 EmitterException::~EmitterException() YAML_CPP_NOEXCEPT = default;
 BadFile::~BadFile() YAML_CPP_NOEXCEPT = default;
+NonUniqueMapKey::~NonUniqueMapKey() YAML_CPP_NOEXCEPT = default;
 }  // namespace YAML
diff --git a/src/node_data.cpp b/src/node_data.cpp
index 6653bc17a..dbfb94191 100644
--- a/src/node_data.cpp
+++ b/src/node_data.cpp
@@ -279,7 +279,12 @@ void node_data::reset_map() {
   m_undefinedPairs.clear();
 }
 
-void node_data::insert_map_pair(node& key, node& value) {
+void node_data::insert_map_pair(node& key, node& value, bool force) {
+  if (!force && !key.scalar().empty())
+    for (const auto& mapEntry : m_map)
+      if (mapEntry.first->scalar() == key.scalar())
+        throw NonUniqueMapKey(m_mark, key);
+
   m_map.emplace_back(&key, &value);
 
   if (!key.is_defined() || !value.is_defined())
diff --git a/test/integration/load_node_test.cpp b/test/integration/load_node_test.cpp
index 19376a430..d7698434c 100644
--- a/test/integration/load_node_test.cpp
+++ b/test/integration/load_node_test.cpp
@@ -465,6 +465,9 @@ TEST(LoadNodeTest, IncorrectSeqEnd) {
   EXPECT_THROW(Load("[foo]_bar"), ParserException);
 }
 
+TEST(LoadNodeTest, NonUniqueMapKey) {
+  EXPECT_THROW(Load("{a: A, b: B, a: A}"), NonUniqueMapKey);
+}
 
 }  // namespace
 }  // namespace YAML