diff --git a/ets2panda/parser/ETSparser.cpp b/ets2panda/parser/ETSparser.cpp
index 7847a5b8999cd2fe40f0282da0925000f4794c06..f08fe9a042e4dac3b271e6ec79306ed0282611eb 100644
--- a/ets2panda/parser/ETSparser.cpp
+++ b/ets2panda/parser/ETSparser.cpp
@@ -2132,6 +2132,8 @@ ir::AstNode *ETSParser::ParseAmbientSignature(const lexer::SourcePosition &start
                                               ir::DummyNodeFlag::INDEXER, typeAnno);
     ES2PANDA_ASSERT(dummyNode != nullptr);
     dummyNode->SetRange({startPos, Lexer()->GetToken().End()});
+    Lexer()->NextToken();  // eat return type
+    ambientIndexerSeen_ = true;
     return dummyNode;
 }
 
diff --git a/ets2panda/parser/ETSparser.h b/ets2panda/parser/ETSparser.h
index bd8fcb7b1cf5b5fb2e3d2ae40926037f3d34e8af..c2db7ca3cfb1480f7a634aaf1879347d7726a26e 100644
--- a/ets2panda/parser/ETSparser.h
+++ b/ets2panda/parser/ETSparser.h
@@ -180,6 +180,7 @@ private:
     ArenaVector<ir::Statement *> ParseTopLevelStatements();
     ir::AstNode *HandleAmbientDeclaration(ir::ModifierFlags &memberModifiers,
                                           const std::function<ir::AstNode *(ir::Identifier *)> &parseClassMethod);
+    ir::Statement *CheckDuplicateAmbientIndex(bool ambientIndexerSeen, const lexer::SourcePosition &startPos);
     static bool IsClassMethodModifier(lexer::TokenType type) noexcept;
 
 #ifdef USE_FTW
@@ -458,6 +459,7 @@ private:
     parser::Program *globalProgram_;
     std::vector<ir::AstNode *> insertingNodes_ {};
     std::unique_ptr<util::ImportPathManager> importPathManager_ {nullptr};
+    bool ambientIndexerSeen_ {false};
 };
 
 class ExternalSourceParser {
diff --git a/ets2panda/parser/ETSparserClasses.cpp b/ets2panda/parser/ETSparserClasses.cpp
index 6341e82096dcc4f051cd8e729b45345b9088c7c8..03d4779e7b3bc254a934ddcbc635317cdb06b5e8 100644
--- a/ets2panda/parser/ETSparserClasses.cpp
+++ b/ets2panda/parser/ETSparserClasses.cpp
@@ -332,12 +332,24 @@ ir::AstNode *ETSParser::HandleAmbientDeclaration(ir::ModifierFlags &memberModifi
                 return parseClassMethod(memberName);
             }
         } else {
+            if (auto *dup = CheckDuplicateAmbientIndex(ambientIndexerSeen_, startPosAmbient)) {
+                return dup;
+            }
             return ParseAmbientSignature(startPosAmbient);
         }
     }
     return nullptr;
 }
 
+ir::Statement *ETSParser::CheckDuplicateAmbientIndex(bool ambientIndexerSeen, const lexer::SourcePosition &startPos)
+{
+    if (!ambientIndexerSeen) {
+        return nullptr;
+    }
+    LogError(diagnostic::DUPLICATE_INDEX_SIGNATURE, {}, startPos);
+    return AllocBrokenStatement(startPos);
+}
+
 // Helper method for ir::ModifierFlags ETSParser::ParseClassMethodModifiers(bool seenStatic)
 ir::ModifierFlags ETSParser::ParseClassMethodModifierFlag()
 {
@@ -1056,6 +1068,7 @@ ir::AstNode *ETSParser::ParseInterfaceField()
         fieldModifiers |= ir::ModifierFlags::DECLARE;
         auto property = HandleAmbientDeclaration(fieldModifiers, parseClassMethod);
         if (property != nullptr) {
+            ambientIndexerSeen_ = true;
             return property;
         }
     }
diff --git a/ets2panda/test/parser/ets/interface_mixed_literals.ets b/ets2panda/test/parser/ets/interface_mixed_literals.ets
new file mode 100644
index 0000000000000000000000000000000000000000..675c6ab62b68594d107f0a6e514e75c20758ac86
--- /dev/null
+++ b/ets2panda/test/parser/ets/interface_mixed_literals.ets
@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2024-2025 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+ declare interface Z {
+    [name: string]: string;
+    [456: number]: boolean;
+}
+
+/* @@? 17:12 Error SyntaxError: Index type must be number in index signature. */
+/* @@? 18:5 Error TypeError: Duplicate index signature in interface */
+/* @@? 18:6 Error SyntaxError: Unexpected token, expected ','. */
+/* @@? 18:6 Error SyntaxError: Unexpected token, expected 'private' or identifier. */
+/* @@? 18:9 Error SyntaxError: Identifier expected. */
+/* @@? 18:9 Error SyntaxError: Unexpected token, expected ','. */
+/* @@? 18:9 Error SyntaxError: Unexpected token, expected 'private' or identifier. */
+/* @@? 18:17 Error SyntaxError: Interface fields must have type annotation. */
+/* @@? 18:18 Error SyntaxError: Invalid Type. */
+/* @@? 18:18 Error SyntaxError: Unexpected token, expected ','. */
+/* @@? 18:18 Error SyntaxError: Unexpected token, expected 'private' or identifier. */
+/* @@? 18:20 Error SyntaxError: Identifier expected. */
+/* @@? 18:20 Error SyntaxError: Unexpected token, expected ','. */
+/* @@? 18:20 Error SyntaxError: Unexpected token, expected 'private' or identifier. */
+/* @@? 18:27 Error SyntaxError: Identifier expected. */
\ No newline at end of file
diff --git a/ets2panda/util/diagnostic/semantic.yaml b/ets2panda/util/diagnostic/semantic.yaml
index cd59e9ec84e35644e64de3f533c63c5de23c3e9b..3be121909b5f05ade969c71ffdc29b341e09ab3a 100644
--- a/ets2panda/util/diagnostic/semantic.yaml
+++ b/ets2panda/util/diagnostic/semantic.yaml
@@ -395,6 +395,10 @@ semantic:
   id: 219
   message: "Duplicate accessor definition"
 
+- name: DUPLICATE_INDEX_SIGNATURE
+  id: 392
+  message: "Duplicate index signature in interface"
+
 - name: DUPLICATE_OVERLOADED_NAME
   id: 385
   message: "Duplicate overloaded method."
@@ -1601,7 +1605,6 @@ semantic:
   id: 347
   message: "Wrong operand type for unary expression"
 
-
 graveyard:
 - 8
 - 29