diff --git a/src/ArduinoJson/Json/JsonSerializer.hpp b/src/ArduinoJson/Json/JsonSerializer.hpp
index 8a21af5c..69f25646 100644
--- a/src/ArduinoJson/Json/JsonSerializer.hpp
+++ b/src/ArduinoJson/Json/JsonSerializer.hpp
@@ -68,8 +68,8 @@ class JsonSerializer : public VariantDataVisitor<size_t> {
     return bytesWritten();
   }
 
-  size_t visitString(const char* value, size_t n) {
-    formatter_.writeString(value, n);
+  size_t visitString(JsonString value) {
+    formatter_.writeString(value.c_str(), value.size());
     return bytesWritten();
   }
 
diff --git a/src/ArduinoJson/MsgPack/MsgPackSerializer.hpp b/src/ArduinoJson/MsgPack/MsgPackSerializer.hpp
index 6bce3b5b..37283740 100644
--- a/src/ArduinoJson/MsgPack/MsgPackSerializer.hpp
+++ b/src/ArduinoJson/MsgPack/MsgPackSerializer.hpp
@@ -80,12 +80,14 @@ class MsgPackSerializer : public VariantDataVisitor<size_t> {
   }
 
   size_t visitString(const char* value) {
-    return visitString(value, strlen(value));
+    return visitString(JsonString(value));
   }
 
-  size_t visitString(const char* value, size_t n) {
+  size_t visitString(JsonString value) {
     ARDUINOJSON_ASSERT(value != NULL);
 
+    auto n = value.size();
+
     if (n < 0x20) {
       writeByte(uint8_t(0xA0 + n));
     } else if (n < 0x100) {
@@ -98,7 +100,7 @@ class MsgPackSerializer : public VariantDataVisitor<size_t> {
       writeByte(0xDB);
       writeInteger(uint32_t(n));
     }
-    writeBytes(reinterpret_cast<const uint8_t*>(value), n);
+    writeBytes(reinterpret_cast<const uint8_t*>(value.c_str()), n);
     return bytesWritten();
   }
 
diff --git a/src/ArduinoJson/Variant/JsonVariantVisitor.hpp b/src/ArduinoJson/Variant/JsonVariantVisitor.hpp
index bf7b38fc..1fe8fa3e 100644
--- a/src/ArduinoJson/Variant/JsonVariantVisitor.hpp
+++ b/src/ArduinoJson/Variant/JsonVariantVisitor.hpp
@@ -47,7 +47,7 @@ struct JsonVariantVisitor {
     return TResult();
   }
 
-  TResult visitString(const char*, size_t) {
+  TResult visitString(JsonString) {
     return TResult();
   }
 };
@@ -72,8 +72,8 @@ class VisitorAdapter {
     return visitor_->visitFloat(value);
   }
 
-  result_type visitString(const char* s, size_t n) {
-    return visitor_->visitString(s, n);
+  result_type visitString(JsonString value) {
+    return visitor_->visitString(value);
   }
 
   result_type visitRawString(const char* p, size_t n) {
diff --git a/src/ArduinoJson/Variant/VariantCompare.hpp b/src/ArduinoJson/Variant/VariantCompare.hpp
index 456b7748..09eb38bd 100644
--- a/src/ArduinoJson/Variant/VariantCompare.hpp
+++ b/src/ArduinoJson/Variant/VariantCompare.hpp
@@ -24,8 +24,8 @@ struct Comparer<T, typename enable_if<IsString<T>::value>::type>
 
   explicit Comparer(T value) : rhs(value) {}
 
-  CompareResult visitString(const char* lhs, size_t n) {
-    int i = stringCompare(adaptString(rhs), adaptString(lhs, n));
+  CompareResult visitString(JsonString lhs) {
+    int i = stringCompare(adaptString(rhs), adaptString(lhs));
     if (i < 0)
       return COMPARE_RESULT_GREATER;
     else if (i > 0)
@@ -143,8 +143,8 @@ struct VariantComparer : ComparerBase {
     return reverseResult(comparer);
   }
 
-  CompareResult visitString(const char* lhs, size_t) {
-    Comparer<const char*> comparer(lhs);
+  CompareResult visitString(JsonString lhs) {
+    Comparer<JsonString> comparer(lhs);
     return reverseResult(comparer);
   }
 
diff --git a/src/ArduinoJson/Variant/VariantData.hpp b/src/ArduinoJson/Variant/VariantData.hpp
index a8f23c2f..1d3bc4e7 100644
--- a/src/ArduinoJson/Variant/VariantData.hpp
+++ b/src/ArduinoJson/Variant/VariantData.hpp
@@ -37,12 +37,12 @@ class VariantData {
         return visitor.visitObject(content_.asObject);
 
       case VALUE_IS_LINKED_STRING:
-        return visitor.visitString(content_.asLinkedString,
-                                   strlen(content_.asLinkedString));
+        return visitor.visitString(JsonString(content_.asLinkedString));
 
       case VALUE_IS_OWNED_STRING:
-        return visitor.visitString(content_.asOwnedString->data,
-                                   content_.asOwnedString->length);
+        return visitor.visitString(JsonString(content_.asOwnedString->data,
+                                              content_.asOwnedString->length,
+                                              JsonString::Copied));
 
       case VALUE_IS_RAW_STRING:
         return visitor.visitRawString(content_.asOwnedString->data,
diff --git a/src/ArduinoJson/Variant/VariantDataVisitor.hpp b/src/ArduinoJson/Variant/VariantDataVisitor.hpp
index 553602d9..a2ef3a84 100644
--- a/src/ArduinoJson/Variant/VariantDataVisitor.hpp
+++ b/src/ArduinoJson/Variant/VariantDataVisitor.hpp
@@ -47,7 +47,7 @@ struct VariantDataVisitor {
     return TResult();
   }
 
-  TResult visitString(const char*, size_t) {
+  TResult visitString(JsonString) {
     return TResult();
   }
 };