diff --git a/ets2panda/checker/ets/typeRelationContext.h b/ets2panda/checker/ets/typeRelationContext.h
index ae20ce5ad1ceddc5f13cc6f8e61af4269b365b04..7ba41f94c85585a2607a67f9da63bea20b07c3ff 100644
--- a/ets2panda/checker/ets/typeRelationContext.h
+++ b/ets2panda/checker/ets/typeRelationContext.h
@@ -36,6 +36,7 @@ public:
 
         ES2PANDA_ASSERT(target != nullptr);
         ES2PANDA_ASSERT(node != nullptr);
+        ES2PANDA_ASSERT(source != nullptr);
         if (target->IsETSArrayType() && node->IsArrayExpression()) {
             assignable_ =
                 ValidateArrayTypeInitializerByElement(relation, node->AsArrayExpression(), target->AsETSArrayType());
diff --git a/ets2panda/checker/types/ets/etsFunctionType.cpp b/ets2panda/checker/types/ets/etsFunctionType.cpp
index 58c4ea3ceade56f550d26cb6b0c7efbf58fbbf10..aa13b83f0aef4d229cf105c1bb79219f07e2a784 100644
--- a/ets2panda/checker/types/ets/etsFunctionType.cpp
+++ b/ets2panda/checker/types/ets/etsFunctionType.cpp
@@ -80,6 +80,7 @@ static ETSObjectType *FunctionTypeToFunctionalInterfaceType(ETSChecker *checker,
         auto nPosParams = arity < sigParamsSize ? arity : sigParamsSize;
         auto *functionN = checker->GlobalBuiltinFunctionType(nPosParams, true);
         auto substitution = Substitution {};
+        ES2PANDA_ASSERT(functionN != nullptr);
         for (size_t i = 0; i < nPosParams; i++) {
             substitution.emplace(functionN->TypeArguments()[i]->AsETSTypeParameter(),
                                  checker->MaybeBoxType(signature->Params()[i]->TsType()));
diff --git a/ets2panda/checker/types/typeRelation.cpp b/ets2panda/checker/types/typeRelation.cpp
index d6de75572207b5695a3c3cba510f209f23562674..57a356d80224dd4522e8a0b27a86ce0790f1fbbe 100644
--- a/ets2panda/checker/types/typeRelation.cpp
+++ b/ets2panda/checker/types/typeRelation.cpp
@@ -154,6 +154,8 @@ bool TypeRelation::IsAssignableTo(Type *source, Type *target)
 bool TypeRelation::IsComparableTo(Type *source, Type *target)
 {
     result_ = CacheLookup(source, target, checker_->ComparableResults(), RelationType::COMPARABLE);
+    ES2PANDA_ASSERT(source != nullptr);
+    ES2PANDA_ASSERT(target != nullptr);
     if (result_ == RelationResult::CACHE_MISS) {
         if (IsAssignableTo(source, target)) {
             return true;
diff --git a/ets2panda/declgen_ets2ts/declgenEts2Ts.cpp b/ets2panda/declgen_ets2ts/declgenEts2Ts.cpp
index b37db2b236f96d3b8f9923b6765675a1381de2ff..0ce3a8f2e9e22c5f5df9a3c9839ec527b98dd93e 100644
--- a/ets2panda/declgen_ets2ts/declgenEts2Ts.cpp
+++ b/ets2panda/declgen_ets2ts/declgenEts2Ts.cpp
@@ -1656,6 +1656,7 @@ bool TSDeclGen::GenInterfaceProp(const ir::MethodDefinition *methodDef)
         OutDts("?");
     }
     OutDts(": ");
+    ES2PANDA_ASSERT(methodDef->Function() != nullptr);
     GenType(methodDef->Function()->Signature()->ReturnType());
     OutDts(";");
     OutEndlDts();