diff --git a/ets2panda/lexer/scripts/keywords.yaml b/ets2panda/lexer/scripts/keywords.yaml
index de7a45f209674d90d71aeedeb1bffe0ec8010011..800f183c3b0f40d6893a4360ae338b457934473b 100644
--- a/ets2panda/lexer/scripts/keywords.yaml
+++ b/ets2panda/lexer/scripts/keywords.yaml
@@ -68,9 +68,9 @@ keywords:
   - name: 'bigint'
     token: KEYW_BIGINT
     keyword_like: [ets, ts]
-    flags: [definable_type_name]
+    flags: [predefined_type]
 
-  - name: 'Bigint'
+  - name: 'BigInt'
     token: KEYW_BUILTIN_BIGINT
     keyword_like: [ets]
     flags:  [predefined_type]
@@ -79,7 +79,7 @@ keywords:
     token: KEYW_BOOLEAN
     keyword: [ets]
     keyword_like: [js, ts]
-    flags: [reserved_type_name, definable_type_name]
+    flags: [reserved_type_name, predefined_type]
 
   - name: 'Boolean'
     token: KEYW_BUILTIN_BOOLEAN
@@ -94,7 +94,7 @@ keywords:
   - name: 'byte'
     token: KEYW_BYTE
     keyword: [ets]
-    flags: [reserved_type_name, definable_type_name]
+    flags: [reserved_type_name, predefined_type]
 
   - name: 'Byte'
     token: KEYW_BUILTIN_BYTE
@@ -114,7 +114,7 @@ keywords:
   - name: 'char'
     token: KEYW_CHAR
     keyword: [ets]
-    flags: [reserved_type_name, definable_type_name]
+    flags: [reserved_type_name, predefined_type]
 
   - name: 'Char'
     token: KEYW_BUILTIN_CHAR
@@ -168,7 +168,7 @@ keywords:
   - name: 'double'
     token: KEYW_DOUBLE
     keyword: [ets]
-    flags: [reserved_type_name, definable_type_name]
+    flags: [reserved_type_name, predefined_type]
 
   - name: 'Double'
     token: KEYW_BUILTIN_DOUBLE
@@ -229,7 +229,7 @@ keywords:
   - name: 'float'
     token: KEYW_FLOAT
     keyword: [ets]
-    flags: [reserved_type_name, definable_type_name]
+    flags: [reserved_type_name, predefined_type]
 
   - name: 'Float'
     token: KEYW_BUILTIN_FLOAT
@@ -319,7 +319,7 @@ keywords:
   - name: 'int'
     token: KEYW_INT
     keyword: [ets]
-    flags: [reserved_type_name, definable_type_name]
+    flags: [reserved_type_name, predefined_type]
 
   - name: 'Int'
     token: KEYW_BUILTIN_INT
@@ -350,7 +350,7 @@ keywords:
   - name: 'long'
     token: KEYW_LONG
     keyword: [ets]
-    flags: [reserved_type_name, definable_type_name]
+    flags: [reserved_type_name, predefined_type]
 
   - name: 'Long'
     token: KEYW_BUILTIN_LONG
@@ -474,7 +474,7 @@ keywords:
   - name: 'short'
     token: KEYW_SHORT
     keyword: [ets]
-    flags: [reserved_type_name, definable_type_name]
+    flags: [reserved_type_name, predefined_type]
 
   - name: 'Short'
     token: KEYW_BUILTIN_SHORT
@@ -488,7 +488,7 @@ keywords:
   - name: 'string'
     token: KEYW_STRING
     keyword_like: [ets, ts]
-    flags: [definable_type_name]
+    flags: [predefined_type]
 
   - name: 'String'
     token: KEYW_BUILTIN_STRING
@@ -498,7 +498,7 @@ keywords:
   - name: 'struct'
     token: KEYW_STRUCT
     keyword_like: [ets]
-    flags: [definable_type_name]
+    flags: [reserved_type_name]
 
   - name: 'super'
     token: KEYW_SUPER
@@ -584,7 +584,7 @@ keywords:
   - name: 'void'
     token: KEYW_VOID
     keyword: [as, ets, js, ts]
-    flags: [unary, reserved_type_name, definable_type_name]
+    flags: [unary, reserved_type_name, predefined_type]
 
   - name: 'while'
     token: KEYW_WHILE
diff --git a/ets2panda/parser/ETSparser.cpp b/ets2panda/parser/ETSparser.cpp
index d9970074638f4d87b7610d70336eedddf0b3a7ca..7847a5b8999cd2fe40f0282da0925000f4794c06 100644
--- a/ets2panda/parser/ETSparser.cpp
+++ b/ets2panda/parser/ETSparser.cpp
@@ -99,6 +99,11 @@ bool ETSParser::IsETSParser() const noexcept
     return true;
 }
 
+bool ETSParser::IsValidIdentifierName(const lexer::Token &token) const noexcept
+{
+    return !token.IsPredefinedType() || util::Helpers::IsStdLib(GetProgram());
+}
+
 std::unique_ptr<lexer::Lexer> ETSParser::InitLexer(const SourceFile &sourceFile)
 {
     GetProgram()->SetSource(sourceFile);
@@ -1078,7 +1083,7 @@ ir::TypeNode *ETSParser::ParseBaseTypeReference(TypeAnnotationParsingOptions *op
 
 ir::TypeNode *ETSParser::ParseLiteralIdent(TypeAnnotationParsingOptions *options)
 {
-    if (Lexer()->GetToken().IsDefinableTypeName()) {
+    if (Lexer()->GetToken().IsPredefinedType()) {
         return GetTypeAnnotationOfPrimitiveType(Lexer()->GetToken().KeywordType(), options);
     }
 
diff --git a/ets2panda/parser/ETSparser.h b/ets2panda/parser/ETSparser.h
index 4e528d725fbac7789f8d80ac635e6d349ebf2aaa..bd8fcb7b1cf5b5fb2e3d2ae40926037f3d34e8af 100644
--- a/ets2panda/parser/ETSparser.h
+++ b/ets2panda/parser/ETSparser.h
@@ -66,6 +66,9 @@ public:
     }
 
     [[nodiscard]] bool IsETSParser() const noexcept override;
+
+    [[nodiscard]] bool IsValidIdentifierName(const lexer::Token &token) const noexcept override;
+
     void AddDirectImportsToDirectExternalSources(const ArenaVector<util::StringView> &directImportsFromMainSource,
                                                  parser::Program *newProg) const;
     bool CheckDupAndReplace(Program *&oldProg, Program *newProg) const;
diff --git a/ets2panda/parser/parserImpl.cpp b/ets2panda/parser/parserImpl.cpp
index 409e4ef4f6243cd88770cfcd40abca7e363f13dd..b9be71ce60be6a99817c0cc0315ab8f11f87e1a9 100644
--- a/ets2panda/parser/parserImpl.cpp
+++ b/ets2panda/parser/parserImpl.cpp
@@ -1334,8 +1334,7 @@ ir::Identifier *ParserImpl::ExpectIdentifier([[maybe_unused]] bool isReference,
     }
 
     auto const &tokenStart = token.Start();
-    if (token.IsPredefinedType() && !util::Helpers::IsStdLib(program_) &&
-        ((options & TypeAnnotationParsingOptions::ADD_TYPE_PARAMETER_BINDING) == 0)) {
+    if (!IsValidIdentifierName(token) && ((options & TypeAnnotationParsingOptions::ADD_TYPE_PARAMETER_BINDING) == 0)) {
         LogError(diagnostic::PREDEFINED_TYPE_AS_IDENTIFIER, {token.Ident()}, tokenStart);
         lexer_->NextToken();
         return AllocBrokenExpression(tokenStart);
diff --git a/ets2panda/parser/parserImpl.h b/ets2panda/parser/parserImpl.h
index ac2c58b6862cc2a0bc2a7a9404dbf072f85d75a6..83ee66ad7bcee45602b6b38df169937e916fe117 100644
--- a/ets2panda/parser/parserImpl.h
+++ b/ets2panda/parser/parserImpl.h
@@ -84,6 +84,11 @@ public:
         return false;
     }
 
+    [[nodiscard]] virtual bool IsValidIdentifierName([[maybe_unused]] const lexer::Token &token) const noexcept
+    {
+        return true;
+    }
+
     ETSParser *AsETSParser()
     {
         ES2PANDA_ASSERT(IsETSParser());
diff --git a/ets2panda/test/ast/parser/ets/InvalidParserImpl.ets b/ets2panda/test/ast/parser/ets/InvalidParserImpl.ets
index feca6d13fffc6c08f84198aede31717936a7c022..899de53972fe0f73745efbef8c0b7f314b523183 100644
--- a/ets2panda/test/ast/parser/ets/InvalidParserImpl.ets
+++ b/ets2panda/test/ast/parser/ets/InvalidParserImpl.ets
@@ -25,6 +25,4 @@ class int {}
 /* @@? 17:12 Error TypeError: Getter must return a value */
 /* @@? 18:5 Error SyntaxError: Getter must not have formal parameters. */
 /* @@? 19:1 Error SyntaxError: Setter must have exactly one formal parameter. */
-/* @@? 23:7 Error SyntaxError: Cannot be used as user-defined type. */
-/* @@? 23:7 Error SyntaxError: Hard keyword 'int' cannot be used as identifier */
-/* @@? 23:7 Error SyntaxError: Identifier expected, got 'int'. */
+/* @@? 23:7 Error SyntaxError: int is a predefined type, cannot be used as an identifier */
diff --git a/ets2panda/test/ast/parser/ets/ambient_indexer_3.ets b/ets2panda/test/ast/parser/ets/ambient_indexer_3.ets
index efd4f356c643e8cf69cad05f4cdb27638295dc55..4f06b3693e3fbd2a9b19aac40a6f7a13b882b374 100644
--- a/ets2panda/test/ast/parser/ets/ambient_indexer_3.ets
+++ b/ets2panda/test/ast/parser/ets/ambient_indexer_3.ets
@@ -29,4 +29,4 @@ function main() {
 /* @@? 17:20 Error SyntaxError: Return type of index signature from exported class or interface need to be identifier. */
 /* @@? 17:20 Error SyntaxError: Unexpected token ']'. */
 /* @@? 17:22 Error SyntaxError: Unexpected token ':'. */
-/* @@? 17:30 Error SyntaxError: Field type annotation expected. */
+/* @@? 17:24 Error SyntaxError: string is a predefined type, cannot be used as an identifier */
diff --git a/ets2panda/test/ast/parser/ets/circular_type_in_alias.ets b/ets2panda/test/ast/parser/ets/circular_type_in_alias.ets
index b951ba4ff5a95559f1109f4171310c46b0719362..09a0912afdb078b51efeb8e558a248d3b9c6d2fc 100644
--- a/ets2panda/test/ast/parser/ets/circular_type_in_alias.ets
+++ b/ets2panda/test/ast/parser/ets/circular_type_in_alias.ets
@@ -29,8 +29,8 @@ type Loop<T, U extends Loop<T, U>> = {
 /* @@? 17:23 Error TypeError: Indexed signatures are not allowed. Use arrays instead! */
 /* @@? 17:24 Error SyntaxError: Unexpected token ']'. */
 /* @@? 17:26 Error SyntaxError: Unexpected token 'extends'. */
-/* @@? 17:34 Error SyntaxError: Unexpected token 'boolean'. */
+/* @@? 17:34 Error SyntaxError: boolean is a predefined type, cannot be used as an identifier */
 /* @@? 17:42 Error SyntaxError: Unexpected token '?'. */
 /* @@? 17:44 Error SyntaxError: number is a predefined type, cannot be used as an identifier */
 /* @@? 17:51 Error SyntaxError: Unexpected token ':'. */
-/* @@? 17:59 Error SyntaxError: Field type annotation expected. */
\ No newline at end of file
+/* @@? 17:53 Error SyntaxError: string is a predefined type, cannot be used as an identifier */
diff --git a/ets2panda/test/ast/parser/ets/typenode_clone_comprehensive.ets b/ets2panda/test/ast/parser/ets/typenode_clone_comprehensive.ets
index a741c2a82c83d4a6d0084dcdb401c2acf676927f..069c51fb2f2b65c77959c4bb1af9b5001bce86c7 100644
--- a/ets2panda/test/ast/parser/ets/typenode_clone_comprehensive.ets
+++ b/ets2panda/test/ast/parser/ets/typenode_clone_comprehensive.ets
@@ -94,7 +94,7 @@ declare const test3: ComplexType<'b'>;
 /* @@? 41:43 Error SyntaxError: Unexpected token ']'. */
 /* @@? 41:43 Error SyntaxError: Field type annotation expected. */
 /* @@? 41:44 Error SyntaxError: Unexpected token ':'. */
-/* @@? 41:52 Error SyntaxError: Field type annotation expected. */
+/* @@? 41:46 Error SyntaxError: string is a predefined type, cannot be used as an identifier  */
 /* @@? 44:41 Error TypeError: The `keyof` keyword can only be used for class or interface type. */
 /* @@? 44:60 Error SyntaxError: Unexpected token, expected ']'. */
 /* @@? 54:34 Error TypeError: Cannot find type 'InvalidMap'. */
diff --git a/ets2panda/test/ast/parser/ets/user_defined_20.ets b/ets2panda/test/ast/parser/ets/user_defined_20.ets
index 2826718e9bcbdc71d589e1ce4e54c2731efef3c4..11c00c085ab04a1aaa9a32c9f8aa67f3a774f110 100644
--- a/ets2panda/test/ast/parser/ets/user_defined_20.ets
+++ b/ets2panda/test/ast/parser/ets/user_defined_20.ets
@@ -17,6 +17,5 @@ struct bigint{
   a : string = "15";
 }
 
-/* @@? 16:8 Error SyntaxError: Cannot be used as user-defined type. */
+/* @@? 16:8 Error SyntaxError: bigint is a predefined type, cannot be used as an identifier */
 /* @@? 16:1 Error TypeError: Structs are only used to define UI components, it should be translated at 'plugin after parser' phase. */
-/* @@? 1:3 Error TypeError: Variable 'bigint' is already defined with different type. */
diff --git a/ets2panda/test/ast/parser/ets/user_defined_21.ets b/ets2panda/test/ast/parser/ets/user_defined_21.ets
index 6ed80976387fa0f0f4fe3a265d75d1bcc98ea334..a7715989bf1d418e8d4c0263dca804341ef44563 100644
--- a/ets2panda/test/ast/parser/ets/user_defined_21.ets
+++ b/ets2panda/test/ast/parser/ets/user_defined_21.ets
@@ -17,5 +17,4 @@ class /* @@ label */bigint{
   a : string = "15";
 }
 
-/* @@@ label Error SyntaxError: Cannot be used as user-defined type.  */
-/* @@? 1:3 Error TypeError: Variable 'bigint' is already defined with different type. */
+/* @@@ label Error SyntaxError: bigint is a predefined type, cannot be used as an identifier */
diff --git a/ets2panda/test/ast/parser/ets/user_defined_5.ets b/ets2panda/test/ast/parser/ets/user_defined_5.ets
index 54076098618908af969d791ce536c4b67d49c011..a20b8680d4ed2d7c4dac1f52b113a95206279b00 100644
--- a/ets2panda/test/ast/parser/ets/user_defined_5.ets
+++ b/ets2panda/test/ast/parser/ets/user_defined_5.ets
@@ -17,6 +17,4 @@ enum /* @@ label */double {
     A, B, C
 }
 
-/* @@@ label Error SyntaxError: Cannot be used as user-defined type. */
-/* @@@ label Error SyntaxError: Identifier expected, got 'double'. */
-/* @@@ label Error SyntaxError: Hard keyword 'double' cannot be used as identifier */
+/* @@@ label Error SyntaxError:  double is a predefined type, cannot be used as an identifier */
diff --git a/ets2panda/test/ast/parser/ets/user_defined_7.ets b/ets2panda/test/ast/parser/ets/user_defined_7.ets
index 587457df03a00716aa658dc94de604c15c31a1a7..5b9519508f6746008b811c5d0d2d3eefcc2cb2d7 100644
--- a/ets2panda/test/ast/parser/ets/user_defined_7.ets
+++ b/ets2panda/test/ast/parser/ets/user_defined_7.ets
@@ -17,9 +17,7 @@ interface /* @@ label1 */double {
     name : string /* @@ label2 */= /* @@ label3 */""
 /* @@ label4 */}
 
-/* @@@ label1 Error SyntaxError: Cannot be used as user-defined type. */
-/* @@@ label1 Error SyntaxError: Identifier expected, got 'double'. */
-/* @@@ label1 Error SyntaxError: Hard keyword 'double' cannot be used as identifier */
+/* @@@ label1 Error SyntaxError: double is a predefined type, cannot be used as an identifier */
 /* @@@ label2 Error SyntaxError: Interface member initialization is prohibited. */
 /* @@@ label3 Error SyntaxError: Unexpected token, expected ','. */
 /* @@? 17:51 Error SyntaxError: Unexpected token, expected 'private' or identifier. */
diff --git a/ets2panda/test/ast/parser/ets/user_defined_8.ets b/ets2panda/test/ast/parser/ets/user_defined_8.ets
index 95556fc08294ee82fbe20c09051086b5d7fad317..52278742dd3f8ed2e018321cb303a067e5bcf713 100644
--- a/ets2panda/test/ast/parser/ets/user_defined_8.ets
+++ b/ets2panda/test/ast/parser/ets/user_defined_8.ets
@@ -17,7 +17,5 @@ struct string{
   a : string = "15";
 }
 
-/* @@? 16:8 Error SyntaxError: Cannot be used as user-defined type. */
+/* @@? 16:8 Error SyntaxError: string is a predefined type, cannot be used as an identifier */
 /* @@? 16:1 Error TypeError: Structs are only used to define UI components, it should be translated at 'plugin after parser' phase. */
-/* @@? 1:3 Error TypeError: Variable 'string' is already defined with different type. */
-/* @@? 17:16 Error TypeError: Type '"15"' cannot be assigned to type 'string' */
diff --git a/ets2panda/test/ast/parser/ets/user_defined_9.ets b/ets2panda/test/ast/parser/ets/user_defined_9.ets
index fecbee124f116921c19898efd6baa1ed741fd7bf..1170c80f98c44b47ee10471aed582e5cd53019a1 100644
--- a/ets2panda/test/ast/parser/ets/user_defined_9.ets
+++ b/ets2panda/test/ast/parser/ets/user_defined_9.ets
@@ -17,6 +17,4 @@ class /* @@ label */string{
   a : string = "15";
 }
 
-/* @@@ label Error SyntaxError: Cannot be used as user-defined type.  */
-/* @@? 1:3 Error TypeError: Variable 'string' is already defined with different type. */
-/* @@? 17:16 Error TypeError: Type '"15"' cannot be assigned to type 'string' */
+/* @@@ label Error SyntaxError: string is a predefined type, cannot be used as an identifier  */