Index: clang-tools-extra/trunk/clang-tidy/modernize/UseNullptrCheck.cpp
===================================================================
--- clang-tools-extra/trunk/clang-tidy/modernize/UseNullptrCheck.cpp
+++ clang-tools-extra/trunk/clang-tidy/modernize/UseNullptrCheck.cpp
@@ -200,12 +200,14 @@
       return true;
     }
 
-    if (!FirstSubExpr)
-      FirstSubExpr = C->getSubExpr()->IgnoreParens();
-
-    // Ignore the expr if it is already a nullptr literal expr.
-    if (isa<CXXNullPtrLiteralExpr>(FirstSubExpr))
+    auto* CastSubExpr = C->getSubExpr()->IgnoreParens();
+    // Ignore cast expressions which cast nullptr literal.
+    if (isa<CXXNullPtrLiteralExpr>(CastSubExpr)) {
       return true;
+    }
+
+    if (!FirstSubExpr)
+      FirstSubExpr = CastSubExpr;
 
     if (C->getCastKind() != CK_NullToPointer &&
         C->getCastKind() != CK_NullToMemberPointer) {
Index: clang-tools-extra/trunk/test/clang-tidy/modernize-use-nullptr.cpp
===================================================================
--- clang-tools-extra/trunk/test/clang-tidy/modernize-use-nullptr.cpp
+++ clang-tools-extra/trunk/test/clang-tidy/modernize-use-nullptr.cpp
@@ -261,3 +261,17 @@
 void IgnoreSubstTemplateType() {
   TemplateClass<int*> a(1);
 }
+
+// Test on casting nullptr.
+struct G {
+  explicit G(bool, const char * = NULL) {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:35: warning: use nullptr
+  // CHECK-FIXES: explicit G(bool, const char * = nullptr) {}
+};
+bool g(const char*);
+void test_cast_nullptr() {
+  G(g(nullptr));
+  G(g((nullptr)));
+  G(g(static_cast<char*>(nullptr)));
+  G(g(static_cast<const char*>(nullptr)));
+}