diff --git a/src/io/BufferedOutputStream.cxx b/src/io/BufferedOutputStream.cxx
index 90ee0ba6e..f63ed7f0b 100644
--- a/src/io/BufferedOutputStream.cxx
+++ b/src/io/BufferedOutputStream.cxx
@@ -9,7 +9,6 @@
 #include <cstdarg>
 
 #include <string.h>
-#include <stdio.h>
 
 #ifdef _UNICODE
 #include "system/Error.hxx"
@@ -52,48 +51,6 @@ BufferedOutputStream::Write(const char *p)
 	Write(p, strlen(p));
 }
 
-void
-BufferedOutputStream::Format(const char *fmt, ...)
-{
-	auto r = buffer.Write();
-	if (r.empty()) {
-		Flush();
-		r = buffer.Write();
-	}
-
-	/* format into the buffer */
-	std::va_list ap;
-	va_start(ap, fmt);
-	std::size_t size = vsnprintf((char *)r.data(), r.size(), fmt, ap);
-	va_end(ap);
-
-	if (size >= r.size()) [[unlikely]] {
-		/* buffer was not large enough; flush it and try
-		   again */
-
-		Flush();
-
-		r = buffer.Write();
-
-		if (size >= r.size()) [[unlikely]] {
-			/* still not enough space: grow the buffer and
-			   try again */
-			++size;
-			r = {buffer.Write(size), size};
-		}
-
-		/* format into the new buffer */
-		va_start(ap, fmt);
-		size = vsnprintf((char *)r.data(), r.size(), fmt, ap);
-		va_end(ap);
-
-		/* this time, it must fit */
-		assert(size < r.size());
-	}
-
-	buffer.Append(size);
-}
-
 void
 BufferedOutputStream::VFmt(fmt::string_view format_str, fmt::format_args args)
 {
diff --git a/src/io/BufferedOutputStream.hxx b/src/io/BufferedOutputStream.hxx
index 7f392d80f..5395fc452 100644
--- a/src/io/BufferedOutputStream.hxx
+++ b/src/io/BufferedOutputStream.hxx
@@ -4,7 +4,6 @@
 #ifndef BUFFERED_OUTPUT_STREAM_HXX
 #define BUFFERED_OUTPUT_STREAM_HXX
 
-#include "util/Compiler.h"
 #include "util/DynamicFifoBuffer.hxx"
 
 #include <fmt/core.h>
@@ -65,12 +64,6 @@ public:
 	 */
 	void Write(const char *p);
 
-	/**
-	 * Write a printf-style formatted string.
-	 */
-	gcc_printf(2,3)
-	void Format(const char *fmt, ...);
-
 	void VFmt(fmt::string_view format_str, fmt::format_args args);
 
 	template<typename S, typename... Args>