diff --git a/src/ContextUtils.cpp b/src/ContextUtils.cpp
index 60ab4591..f5c5b9d8 100644
--- a/src/ContextUtils.cpp
+++ b/src/ContextUtils.cpp
@@ -57,7 +57,7 @@ static std::string nameForContext(DeclContext *context)
         return rec->getNameAsString();
     } else if (auto *method = dyn_cast<CXXMethodDecl>(context)) {
         return method->getNameAsString();
-    } else if (dyn_cast<TranslationUnitDecl>(context)) {
+    } else if (isa<TranslationUnitDecl>(context)) {
         return {};
     } else {
         llvm::errs() << "Unhandled kind: " << context->getDeclKindName() << "\n";
diff --git a/src/ContextUtils.h b/src/ContextUtils.h
index def281a5..4be8c219 100644
--- a/src/ContextUtils.h
+++ b/src/ContextUtils.h
@@ -55,7 +55,7 @@ namespace clazy
 inline bool isValueDeclInFunctionContext(const clang::ValueDecl *valueDecl)
 {
     const auto *context = valueDecl ? valueDecl->getDeclContext() : nullptr;
-    return context && llvm::isa<clang::FunctionDecl>(context) && !llvm::isa<clang::ParmVarDecl>(valueDecl);
+    return llvm::isa_and_nonnull<clang::FunctionDecl>(context) && !llvm::isa<clang::ParmVarDecl>(valueDecl);
 }
 
 /**
diff --git a/src/checks/level0/strict-iterators.cpp b/src/checks/level0/strict-iterators.cpp
index 3153928d..f05c238f 100644
--- a/src/checks/level0/strict-iterators.cpp
+++ b/src/checks/level0/strict-iterators.cpp
@@ -131,7 +131,7 @@ bool StrictIterators::handleImplicitCast(ImplicitCastExpr *implicitCast)
     }
 
     auto *p = m_context->parentMap->getParent(implicitCast);
-    if (dyn_cast<CXXOperatorCallExpr>(p)) {
+    if (isa<CXXOperatorCallExpr>(p)) {
         return false;
     }
 
diff --git a/src/checks/level0/temporary-iterator.cpp b/src/checks/level0/temporary-iterator.cpp
index 999c3d4a..ba5dbdae 100644
--- a/src/checks/level0/temporary-iterator.cpp
+++ b/src/checks/level0/temporary-iterator.cpp
@@ -146,7 +146,7 @@ void TemporaryIterator::VisitStmt(clang::Stmt *stm)
             }
 
             Stmt *firstChild = clazy::getFirstChild(impl);
-            if (firstChild && isa<ImplicitCastExpr>(firstChild) && dyn_cast<ImplicitCastExpr>(firstChild)->getCastKind() == CK_LValueToRValue) {
+            if (isa_and_nonnull<ImplicitCastExpr>(firstChild) && dyn_cast<ImplicitCastExpr>(firstChild)->getCastKind() == CK_LValueToRValue) {
                 return;
             }
         }