diff --git a/ets2panda/compiler/core/ETSCompiler.cpp b/ets2panda/compiler/core/ETSCompiler.cpp
index 798ec10abff49a3d9d3c353f566e61936261fce9..8992e4463266032d54ade146aee52b4d6f28f6a7 100644
--- a/ets2panda/compiler/core/ETSCompiler.cpp
+++ b/ets2panda/compiler/core/ETSCompiler.cpp
@@ -815,6 +815,7 @@ void ETSCompiler::Compile(const ir::Identifier *expr) const
     ETSGen *etsg = GetETSGen();
 
     auto const *smartType = expr->TsType();
+    ES2PANDA_ASSERT(smartType != nullptr);
     if (smartType->IsETSTypeParameter() || smartType->IsETSPartialTypeParameter() || smartType->IsETSNonNullishType()) {
         smartType = etsg->Checker()->GetApparentType(smartType);
     }
diff --git a/ets2panda/compiler/lowering/ets/lambdaLowering.cpp b/ets2panda/compiler/lowering/ets/lambdaLowering.cpp
index 0c4e4caf52f4d93e039341ad5d7fcbb1173d3042..4bdc0ff953a0817b4c9bfbb3c7a6bf4d27c0cc5a 100644
--- a/ets2panda/compiler/lowering/ets/lambdaLowering.cpp
+++ b/ets2panda/compiler/lowering/ets/lambdaLowering.cpp
@@ -228,6 +228,7 @@ static void ProcessCalleeMethodBody(ir::AstNode *body, checker::ETSChecker *chec
             auto *id = node->AsIdentifier();
             if (auto ref = varMap.find(id->Variable()); ref != varMap.end()) {
                 id->SetVariable(ref->second);
+                id->Check(checker);
             }
         }
         if (substitution == nullptr) {
diff --git a/ets2panda/test/ast/compiler/ets/LambdaParameterWithImplicitType.ets b/ets2panda/test/ast/compiler/ets/LambdaParameterWithImplicitType.ets
new file mode 100644
index 0000000000000000000000000000000000000000..2cde0dd68986def9af9d335f874e106fcd582d0b
--- /dev/null
+++ b/ets2panda/test/ast/compiler/ets/LambdaParameterWithImplicitType.ets
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 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.
+ */
+
+const foo = async (): Promise<Double> => {
+    return 42.0; // Return a double to satisfy the Promise<Double>
+};
+
+foo().then((result) => {                                     // crash - issue #26815
+    console.log(`Async function returned: ${result}`);
+});
+
+let fooArray = ["a", "b", "c"];
+let fooArrayMapped = fooArray.map(x => x + " is mapped");    // crash - issue #26856
+let fooArrayMappedAndChecked = fooArray.map(x => x == "a");  // crash - issue #26856