diff --git a/ext/native/json/json_writer.cpp b/ext/native/json/json_writer.cpp
index ec9019c50d..ec43a4fae8 100644
--- a/ext/native/json/json_writer.cpp
+++ b/ext/native/json/json_writer.cpp
@@ -1,6 +1,9 @@
+#include <iomanip>
 #include "json/json_writer.h"
 
-JsonWriter::JsonWriter() {
+JsonWriter::JsonWriter(int flags) {
+	pretty_ = (flags & PRETTY) != 0;
+	str_.imbue(std::locale::classic());
 }
 
 JsonWriter::~JsonWriter() {
@@ -13,15 +16,24 @@ void JsonWriter::begin() {
 
 void JsonWriter::end() {
 	pop();
-	str_ << "\n";
+	if (pretty_)
+		str_ << "\n";
 }
 
 const char *JsonWriter::indent(int n) const {
-	static const char * const whitespace = "															";
+	if (!pretty_)
+		return "";
+	static const char * const whitespace = "                                ";
+	if (n > 32) {
+		// Avoid crash.
+		return whitespace;
+	}
 	return whitespace + (32 - n);
 }
 
 const char *JsonWriter::indent() const {
+	if (!pretty_)
+		return "";
 	int amount = (int)stack_.size() + 1;
 	amount *= 2;	// 2-space indent.
 	return indent(amount);
@@ -37,7 +49,7 @@ const char *JsonWriter::comma() const {
 	if (stack_.back().first) {
 		return "";
 	} else {
-		return ",";
+		return ",\n";
 	}
 }
 
@@ -45,17 +57,21 @@ const char *JsonWriter::arrayComma() const {
 	if (stack_.back().first) {
 		return "\n";
 	} else {
-		return ", ";
+		return pretty_ ? ", " : ",";
 	}
 }
 
 void JsonWriter::pushDict(const char *name) {
-	str_ << comma() << "\n" << indent() << "\"" << name << "\": {";
+	str_ << comma() << indent() << "\"";
+	writeEscapedString(name);
+	str_ << "\": {";
 	stack_.push_back(StackEntry(DICT));
 }
 
 void JsonWriter::pushArray(const char *name) {
-	str_ << comma() << "\n" << indent() << "\"" << name << "\": [";
+	str_ << comma() << indent() << "\"";
+	writeEscapedString(name);
+	str_ << "\": [";
 	stack_.push_back(StackEntry(ARRAY));
 }
 
@@ -65,7 +81,9 @@ void JsonWriter::writeBool(bool value) {
 }
 
 void JsonWriter::writeBool(const char *name, bool value) {
-	str_ << comma() << "\n" << indent() << "\"" << name << "\": " << (value ? "true" : "false");
+	str_ << comma() << indent() << "\"";
+	writeEscapedString(name);
+	str_ << "\": " << (value ? "true" : "false");
 	stack_.back().first = false;
 }
 
@@ -75,7 +93,9 @@ void JsonWriter::writeInt(int value) {
 }
 
 void JsonWriter::writeInt(const char *name, int value) {
-	str_ << comma() << "\n" << indent() << "\"" << name << "\": " << value;
+	str_ << comma() << indent() << "\"";
+	writeEscapedString(name);
+	str_ << "\": " << value;
 	stack_.back().first = false;
 }
 
@@ -85,31 +105,78 @@ void JsonWriter::writeFloat(double value) {
 }
 
 void JsonWriter::writeFloat(const char *name, double value) {
-	str_ << comma() << "\n" << indent() << "\"" << name << "\": " << value;
+	str_ << comma() << indent() << "\"";
+	writeEscapedString(name);
+	str_ << "\": " << value;
 	stack_.back().first = false;
 }
 
 void JsonWriter::writeString(const char *value) {
-	str_ << arrayComma() << arrayIndent() << "\"" << value << "\"";
+	str_ << arrayComma() << arrayIndent() << "\"";
+	writeEscapedString(value);
+	str_ << "\"";
 	stack_.back().first = false;
 }
 
 void JsonWriter::writeString(const char *name, const char *value) {
-	str_ << comma() << "\n" << indent() << "\"" << name << "\": \"" << value << "\"";
+	str_ << comma() << indent() << "\"";
+	writeEscapedString(name);
+	str_ << "\": \"";
+	writeEscapedString(value);
+	str_ << "\"";
 	stack_.back().first = false;
 }
 
 void JsonWriter::pop() {
 	BlockType type = stack_.back().type;
 	stack_.pop_back();
+	if (pretty_)
+		str_ << "\n" << indent();
 	switch (type) {
 	case ARRAY:
-		str_ << "\n" << indent() << "]";
+		str_ << "]";
 		break;
 	case DICT:
-		str_ << "\n" << indent() << "}";
+		str_ << "}";
 		break;
 	}
 	if (stack_.size() > 0)
 		stack_.back().first = false;
 }
+
+void JsonWriter::writeEscapedString(const char *str) {
+	size_t pos = 0;
+	size_t len = strlen(str);
+
+	auto update = [&](size_t current, size_t skip = 0) {
+		size_t end = current;
+		if (pos < end)
+			str_ << std::string(str + pos, end - pos);
+		pos = end + skip;
+	};
+
+	for (size_t i = 0; i < len; ++i) {
+		if (str[i] == '\\' || str[i] == '"' || str[i] == '/') {
+			update(i);
+			str_ << '\\';
+		} else if (str[i] == '\r') {
+			update(i, 1);
+			str_ << "\\r";
+		} else if (str[i] == '\n') {
+			update(i, 1);
+			str_ << "\\n";
+		} else if (str[i] == '\t') {
+			update(i, 1);
+			str_ << "\\t";
+		} else if (str[i] < 32) {
+			update(i, 1);
+			str_ << "\\u" << std::hex << std::setw(4) << std::setfill('0') << (int)str[i] << std::dec << std::setw(0);
+		}
+	}
+
+	if (pos != 0) {
+		update(len);
+	} else {
+		str_ << str;
+	}
+}
diff --git a/ext/native/json/json_writer.h b/ext/native/json/json_writer.h
index b58ca37f6d..378a09f5b9 100644
--- a/ext/native/json/json_writer.h
+++ b/ext/native/json/json_writer.h
@@ -16,7 +16,7 @@
 
 class JsonWriter {
 public:
-	JsonWriter();
+	JsonWriter(int flags = NORMAL);
 	~JsonWriter();
 	void begin();
 	void end();
@@ -31,17 +31,33 @@ public:
 	void writeFloat(const char *name, double value);
 	void writeString(const char *value);
 	void writeString(const char *name, const char *value);
+	void writeString(const std::string &value) {
+		writeString(value.c_str());
+	}
+	void writeString(const char *name, const std::string &value) {
+		writeString(name, value.c_str());
+	}
+	void writeString(const std::string &name, const std::string &value) {
+		writeString(name.c_str(), value.c_str());
+	}
 
 	std::string str() const {
 		return str_.str();
 	}
 
+	enum {
+		NORMAL = 0,
+		PRETTY = 1,
+	};
+
 private:
 	const char *indent(int n) const;
 	const char *comma() const;
 	const char *arrayComma() const;
 	const char *indent() const;
 	const char *arrayIndent() const;
+	void writeEscapedString(const char *s);
+
 	enum BlockType {
 		ARRAY,
 		DICT,
@@ -53,4 +69,5 @@ private:
 	};
 	std::vector<StackEntry> stack_;
 	std::ostringstream str_;
+	bool pretty_;
 };