diff --git a/src/music/os2_m.cpp b/src/music/os2_m.cpp
index 4736065678..449caf3738 100644
--- a/src/music/os2_m.cpp
+++ b/src/music/os2_m.cpp
@@ -12,6 +12,7 @@
 #include "os2_m.h"
 #include "midifile.hpp"
 #include "../base_media_base.h"
+#include "../3rdparty/fmt/format.h"
 
 #define INCL_DOS
 #define INCL_OS2MM
@@ -36,14 +37,9 @@
  * @param cmd The command to send.
  * @return The result of sending it.
  */
-static long CDECL MidiSendCommand(const char *cmd, ...)
+static long CDECL MidiSendCommand(const std::string_view cmd)
 {
-	va_list va;
-	char buf[512];
-	va_start(va, cmd);
-	vseprintf(buf, lastof(buf), cmd, va);
-	va_end(va);
-	return mciSendString(buf, nullptr, 0, nullptr, 0);
+	return mciSendString(cmd.data(), nullptr, 0, nullptr, 0);
 }
 
 /** OS/2's music player's factory. */
@@ -56,7 +52,7 @@ void MusicDriver_OS2::PlaySong(const MusicSongInfo &song)
 	MidiSendCommand("close all");
 	if (filename.empty()) return;
 
-	if (MidiSendCommand("open %s type sequencer alias song", filename.c_str()) != 0) {
+	if (MidiSendCommand(fmt::format("open {} type sequencer alias song", filename)) != 0) {
 		return;
 	}
 
diff --git a/src/safeguards.h b/src/safeguards.h
index aca461175f..d56b0015a0 100644
--- a/src/safeguards.h
+++ b/src/safeguards.h
@@ -44,7 +44,7 @@
 #define sprintf   SAFEGUARD_DO_NOT_USE_THIS_METHOD
 #define snprintf  SAFEGUARD_DO_NOT_USE_THIS_METHOD
 
-/* Use vseprintf instead. */
+/* Use fmt::format instead. */
 #define vsprintf  SAFEGUARD_DO_NOT_USE_THIS_METHOD
 #define vsnprintf SAFEGUARD_DO_NOT_USE_THIS_METHOD
 
diff --git a/src/string.cpp b/src/string.cpp
index 86170a54b5..ff91f95ca3 100644
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -50,23 +50,6 @@
 #include "safeguards.h"
 #undef vsnprintf
 
-/**
- * Safer implementation of vsnprintf; same as vsnprintf except:
- * - last instead of size, i.e. replace sizeof with lastof.
- * - return gives the amount of characters added, not what it would add.
- * @param str    buffer to write to up to last
- * @param last   last character we may write to
- * @param format the formatting (see snprintf)
- * @param ap     the list of arguments for the format
- * @return the number of added characters
- */
-int CDECL vseprintf(char *str, const char *last, const char *format, va_list ap)
-{
-	ptrdiff_t diff = last - str;
-	if (diff < 0) return 0;
-	return std::min(static_cast<int>(diff), vsnprintf(str, diff + 1, format, ap));
-}
-
 /**
  * Appends characters from one string to another.
  *
@@ -536,10 +519,14 @@ int CDECL vsnprintf(char *str, size_t size, const char *format, va_list ap)
  */
 int CDECL seprintf(char *str, const char *last, const char *format, ...)
 {
+	ptrdiff_t diff = last - str;
+	if (diff < 0) return 0;
+
 	va_list ap;
 
 	va_start(ap, format);
-	int ret = vseprintf(str, last, format, ap);
+	int ret = std::min(static_cast<int>(diff), vsnprintf(str, diff + 1, format, ap));
+
 	va_end(ap);
 	return ret;
 }
diff --git a/src/string_func.h b/src/string_func.h
index 955bfc8bd4..816f85cf57 100644
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -36,7 +36,6 @@ char *strecpy(char *dst, const char *src, const char *last) NOACCESS(3);
 char *stredup(const char *src, const char *last = nullptr) NOACCESS(2);
 
 int CDECL seprintf(char *str, const char *last, const char *format, ...) WARN_FORMAT(3, 4) NOACCESS(2);
-int CDECL vseprintf(char *str, const char *last, const char *format, va_list ap) WARN_FORMAT(3, 0) NOACCESS(2);
 
 std::string FormatArrayAsHex(span<const byte> data);