diff --git a/src/threading/formatters/JSON.cc b/src/threading/formatters/JSON.cc
index 5320b79d70..0a89db329d 100644
--- a/src/threading/formatters/JSON.cc
+++ b/src/threading/formatters/JSON.cc
@@ -22,12 +22,14 @@ namespace zeek::threading::formatter
 	{
 
 // For deprecated NullDoubleWriter
+JSON::NullDoubleWriter::NullDoubleWriter(rapidjson::StringBuffer& stream)
+	: writer(std::make_unique<zeek::json::detail::NullDoubleWriter>(stream))
+	{
+	}
+
 bool JSON::NullDoubleWriter::Double(double d)
 	{
-	if ( rapidjson::internal::Double(d).IsNanOrInf() )
-		return rapidjson::Writer<rapidjson::StringBuffer>::Null();
-
-	return rapidjson::Writer<rapidjson::StringBuffer>::Double(d);
+	return writer->Double(d);
 	}
 
 JSON::JSON(MsgThread* t, TimeFormat tf, bool arg_include_unset_fields)
diff --git a/src/threading/formatters/JSON.h b/src/threading/formatters/JSON.h
index 5703216cd3..74bc89c8ae 100644
--- a/src/threading/formatters/JSON.h
+++ b/src/threading/formatters/JSON.h
@@ -2,6 +2,8 @@
 
 #pragma once
 
+#include <memory>
+
 #define RAPIDJSON_HAS_STDSTRING 1
 // Remove in v7.1 when removing NullDoubleWriter below and also remove
 // rapidjson include tweaks from  CMake's dynamic_plugin_base target.
@@ -46,11 +48,11 @@ public:
 		{
 	public:
 		[[deprecated("Remove in v7.1 - This is an implementation detail.")]] NullDoubleWriter(
-			rapidjson::StringBuffer& stream)
-			: rapidjson::Writer<rapidjson::StringBuffer>(stream)
-			{
-			}
+			rapidjson::StringBuffer& stream);
 		bool Double(double d);
+
+	private:
+		std::unique_ptr<json::detail::NullDoubleWriter> writer;
 		};
 
 private: