diff --git a/src/ArduinoJson/Json/JsonSerializer.hpp b/src/ArduinoJson/Json/JsonSerializer.hpp
index 8fe5a9e9..81abca1c 100644
--- a/src/ArduinoJson/Json/JsonSerializer.hpp
+++ b/src/ArduinoJson/Json/JsonSerializer.hpp
@@ -93,7 +93,7 @@ class JsonSerializer : public VariantDataVisitor<size_t> {
     return bytesWritten();
   }
 
-  size_t visitNull() {
+  size_t visitNull(nullptr_t) {
     formatter_.writeRaw("null");
     return bytesWritten();
   }
diff --git a/src/ArduinoJson/MsgPack/MsgPackSerializer.hpp b/src/ArduinoJson/MsgPack/MsgPackSerializer.hpp
index d6f118fb..323ed90c 100644
--- a/src/ArduinoJson/MsgPack/MsgPackSerializer.hpp
+++ b/src/ArduinoJson/MsgPack/MsgPackSerializer.hpp
@@ -172,7 +172,7 @@ class MsgPackSerializer : public VariantDataVisitor<size_t> {
     return bytesWritten();
   }
 
-  size_t visitNull() {
+  size_t visitNull(nullptr_t) {
     writeByte(0xC0);
     return bytesWritten();
   }
diff --git a/src/ArduinoJson/Variant/JsonVariantVisitor.hpp b/src/ArduinoJson/Variant/JsonVariantVisitor.hpp
index bb16d09e..18ae3f41 100644
--- a/src/ArduinoJson/Variant/JsonVariantVisitor.hpp
+++ b/src/ArduinoJson/Variant/JsonVariantVisitor.hpp
@@ -31,7 +31,7 @@ struct JsonVariantVisitor {
     return TResult();
   }
 
-  TResult visitNull() {
+  TResult visitNull(nullptr_t) {
     return TResult();
   }
 
@@ -92,8 +92,8 @@ class VisitorAdapter {
     return visitor_->visitBoolean(value);
   }
 
-  result_type visitNull() {
-    return visitor_->visitNull();
+  result_type visitNull(nullptr_t) {
+    return visitor_->visitNull(nullptr);
   }
 
  private:
@@ -106,7 +106,7 @@ typename TVisitor::result_type accept(JsonVariantConst variant,
                                       TVisitor& visitor) {
   auto data = VariantAttorney::getData(variant);
   if (!data)
-    return visitor.visitNull();
+    return visitor.visitNull(nullptr);
   auto resources = VariantAttorney::getResourceManager(variant);
   VisitorAdapter<TVisitor> adapter(visitor, resources);
   return data->accept(adapter);
diff --git a/src/ArduinoJson/Variant/VariantCompare.hpp b/src/ArduinoJson/Variant/VariantCompare.hpp
index ca865e64..067be7fc 100644
--- a/src/ArduinoJson/Variant/VariantCompare.hpp
+++ b/src/ArduinoJson/Variant/VariantCompare.hpp
@@ -35,7 +35,7 @@ struct Comparer<T, typename enable_if<IsString<T>::value>::type>
       return COMPARE_RESULT_EQUAL;
   }
 
-  CompareResult visitNull() {
+  CompareResult visitNull(nullptr_t) {
     if (adaptString(rhs).isNull())
       return COMPARE_RESULT_EQUAL;
     else
@@ -69,7 +69,7 @@ struct Comparer<T, typename enable_if<is_integral<T>::value ||
 };
 
 struct NullComparer : ComparerBase {
-  CompareResult visitNull() {
+  CompareResult visitNull(nullptr_t) {
     return COMPARE_RESULT_EQUAL;
   }
 };
@@ -167,7 +167,7 @@ struct VariantComparer : ComparerBase {
     return reverseResult(comparer);
   }
 
-  CompareResult visitNull() {
+  CompareResult visitNull(nullptr_t) {
     NullComparer comparer;
     return reverseResult(comparer);
   }
diff --git a/src/ArduinoJson/Variant/VariantData.hpp b/src/ArduinoJson/Variant/VariantData.hpp
index 5aec374f..8d4f4c15 100644
--- a/src/ArduinoJson/Variant/VariantData.hpp
+++ b/src/ArduinoJson/Variant/VariantData.hpp
@@ -58,7 +58,7 @@ class VariantData {
         return visitor.visitBoolean(content_.asBoolean != 0);
 
       default:
-        return visitor.visitNull();
+        return visitor.visitNull(nullptr);
     }
   }
 
@@ -68,7 +68,7 @@ class VariantData {
     if (var != 0)
       return var->accept(visitor);
     else
-      return visitor.visitNull();
+      return visitor.visitNull(nullptr);
   }
 
   VariantData* addElement(ResourceManager* resources) {
diff --git a/src/ArduinoJson/Variant/VariantDataVisitor.hpp b/src/ArduinoJson/Variant/VariantDataVisitor.hpp
index 01a5da24..b14dd88f 100644
--- a/src/ArduinoJson/Variant/VariantDataVisitor.hpp
+++ b/src/ArduinoJson/Variant/VariantDataVisitor.hpp
@@ -31,7 +31,7 @@ struct VariantDataVisitor {
     return TResult();
   }
 
-  TResult visitNull() {
+  TResult visitNull(nullptr_t) {
     return TResult();
   }