diff --git a/ets2panda/checker/ets/function.cpp b/ets2panda/checker/ets/function.cpp
index fd2d36b35fd451063f215c921ccb2d27627c3726..369d97ec5ea318d4246fc1618c5b89fad115a8ac 100644
--- a/ets2panda/checker/ets/function.cpp
+++ b/ets2panda/checker/ets/function.cpp
@@ -1609,7 +1609,7 @@ static bool AppendSignatureInfoParam(ETSChecker *checker, SignatureInfo *sigInfo
     if (!param->IsOptional()) {
         ++sigInfo->minArgCount;
     }
-    ES2PANDA_ASSERT(!param->IsOptional() ||
+    ES2PANDA_ASSERT(!param->IsOptional() || param->Ident()->TsType()->IsTypeError() ||
                     checker->Relation()->IsSupertypeOf(param->Ident()->TsType(), checker->GlobalETSUndefinedType()));
     return true;
 }
diff --git a/ets2panda/checker/ets/utilityTypeHandlers.cpp b/ets2panda/checker/ets/utilityTypeHandlers.cpp
index 6341a07915301bb57b18aec8fe648f1f1b01d5b0..3bc326155822b3d444b65c31076f1d1d42cf44ae 100644
--- a/ets2panda/checker/ets/utilityTypeHandlers.cpp
+++ b/ets2panda/checker/ets/utilityTypeHandlers.cpp
@@ -525,6 +525,35 @@ void ETSChecker::CreatePartialClassDeclaration(ir::ClassDefinition *const newCla
     newClassDefinition->Variable()->SetTsType(nullptr);
 }
 
+static void SetupFunctionParams(ir::ScriptFunction *function, varbinder::FunctionParamScope *paramScope,
+                                checker::ETSChecker *checker)
+{
+    for (auto *params : function->Params()) {
+        auto *paramExpr = params->AsETSParameterExpression();
+        if (paramExpr->Ident()->TypeAnnotation() == nullptr) {
+            paramExpr->Ident()->SetTsTypeAnnotation(nullptr);
+        } else {
+            auto *unionType =
+                // SUPPRESS_CSA_NEXTLINE(alpha.core.AllocatorETSCheckerHint)
+                checker->ProgramAllocNode<ir::ETSUnionType>(
+                    ArenaVector<ir::TypeNode *>(
+                        {paramExpr->Ident()->TypeAnnotation(),
+                         // SUPPRESS_CSA_NEXTLINE(alpha.core.AllocatorETSCheckerHint)
+                         checker->ProgramAllocNode<ir::ETSUndefinedType>(checker->ProgramAllocator())},
+                        checker->ProgramAllocator()->Adapter()),
+                    checker->ProgramAllocator());
+            paramExpr->Ident()->SetTsTypeAnnotation(unionType);
+            unionType->SetParent(paramExpr->Ident());
+        }
+        auto [paramVar, node] = paramScope->AddParamDecl(checker->ProgramAllocator(), checker->VarBinder(), paramExpr);
+        if (node != nullptr) {
+            checker->VarBinder()->ThrowRedeclaration(node->Start(), paramVar->Name(), paramVar->Declaration()->Type());
+        }
+
+        paramExpr->SetVariable(paramVar);
+    }
+}
+
 // CC-OFFNXT(huge_method[C++], G.FUN.01-CPP) solid logic
 ir::MethodDefinition *ETSChecker::CreateNullishAccessor(ir::MethodDefinition *const accessor,
                                                         ir::TSInterfaceDeclaration *interface)
@@ -572,27 +601,8 @@ ir::MethodDefinition *ETSChecker::CreateNullishAccessor(ir::MethodDefinition *co
                                         ProgramAllocator()->Adapter()),
             ProgramAllocator()));
     } else {
-        for (auto *params : function->Params()) {
-            auto *paramExpr = params->AsETSParameterExpression();
-
-            auto *unionType =
-                // SUPPRESS_CSA_NEXTLINE(alpha.core.AllocatorETSCheckerHint)
-                ProgramAllocNode<ir::ETSUnionType>(
-                    ArenaVector<ir::TypeNode *>({paramExpr->Ident()->TypeAnnotation(),
-                                                 // SUPPRESS_CSA_NEXTLINE(alpha.core.AllocatorETSCheckerHint)
-                                                 ProgramAllocNode<ir::ETSUndefinedType>(ProgramAllocator())},
-                                                ProgramAllocator()->Adapter()),
-                    ProgramAllocator());
-            paramExpr->Ident()->SetTsTypeAnnotation(unionType);
-            unionType->SetParent(paramExpr->Ident());
-
-            auto [paramVar, node] = paramScope->AddParamDecl(ProgramAllocator(), VarBinder(), paramExpr);
-            if (node != nullptr) {
-                VarBinder()->ThrowRedeclaration(node->Start(), paramVar->Name(), paramVar->Declaration()->Type());
-            }
-
-            paramExpr->SetVariable(paramVar);
-        }
+        // SUPPRESS_CSA_NEXTLINE(alpha.core.AllocatorETSCheckerHint)
+        SetupFunctionParams(function, paramScope, this);
     }
 
     nullishAccessor->SetOverloads(ArenaVector<ir::MethodDefinition *>(ProgramAllocator()->Adapter()));
diff --git a/ets2panda/compiler/lowering/ets/defaultParametersLowering.cpp b/ets2panda/compiler/lowering/ets/defaultParametersLowering.cpp
index 901046c0779895a5ad1c2f3ea9c424f54a5eefae..2c7afb91de09f6858c4fe0525b746f225d4ed6b4 100644
--- a/ets2panda/compiler/lowering/ets/defaultParametersLowering.cpp
+++ b/ets2panda/compiler/lowering/ets/defaultParametersLowering.cpp
@@ -98,6 +98,7 @@ static void TransformFunction(public_lib::Context *ctx, ir::ScriptFunction *func
         }
         if (param->AsETSParameterExpression()->TypeAnnotation() == nullptr) {  // #23134
             ES2PANDA_ASSERT(ctx->diagnosticEngine->IsAnyError());
+            param->AsETSParameterExpression()->SetInitializer(nullptr);
             continue;
         }
         defaultParams.push_back(param->AsETSParameterExpression());
diff --git a/ets2panda/test/ast/compiler/ets/type_error_processing/param_typeannotation_null.ets b/ets2panda/test/ast/compiler/ets/type_error_processing/param_typeannotation_null.ets
new file mode 100644
index 0000000000000000000000000000000000000000..e23f26a1e73d09f55811c7adb00e3db7161d0a8f
--- /dev/null
+++ b/ets2panda/test/ast/compiler/ets/type_error_processing/param_typeannotation_null.ets
@@ -0,0 +1,24 @@
+/*
+ * 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.
+ */
+
+interface inter <T>{
+    get value(): Double;
+    set value(A = Int.MAX_VALUE + 1);
+}
+
+function foo(i: Partial<inter<String>>): void {}
+
+/* @@? 18:15 Error TypeError: The type of parameter 'A' cannot be inferred */
+/* @@? 18:17 Error SyntaxError: Parameter declaration should have an explicit type annotation. */