diff --git a/modules/gdscript/gd_parser.cpp b/modules/gdscript/gd_parser.cpp
index 031f106df0b..4a36fbb4f1d 100644
--- a/modules/gdscript/gd_parser.cpp
+++ b/modules/gdscript/gd_parser.cpp
@@ -724,6 +724,7 @@ GDParser::Node* GDParser::_parse_expression(Node *p_parent,bool p_static,bool p_
 			};
 
 			Node *key=NULL;
+			Set<Variant> keys;
 
 			DictExpect expecting=DICT_EXPECT_KEY;
 
@@ -819,6 +820,16 @@ GDParser::Node* GDParser::_parse_expression(Node *p_parent,bool p_static,bool p_
 							return NULL;
 						expecting=DICT_EXPECT_COMMA;
 
+						if (key->type == GDParser::Node::TYPE_CONSTANT) {
+							Variant const& keyName = static_cast<const GDParser::ConstantNode*>(key)->value;
+
+							if (keys.has(keyName)) {
+								_set_error("Duplicate key found in Dictionary literal");
+								return NULL;
+							}
+							keys.insert(keyName);
+						}
+
 						DictionaryNode::Pair pair;
 						pair.key=key;
 						pair.value=value;