diff --git a/Source/DiabloUI/diabloui.cpp b/Source/DiabloUI/diabloui.cpp
index 27d8bca8a..2681e2550 100644
--- a/Source/DiabloUI/diabloui.cpp
+++ b/Source/DiabloUI/diabloui.cpp
@@ -3,8 +3,6 @@
 #include <algorithm>
 #include <string>
 
-#include <fmt/compile.h>
-
 #include "DiabloUI/art_draw.h"
 #include "DiabloUI/button.h"
 #include "DiabloUI/dialogs.h"
@@ -28,6 +26,7 @@
 #include "utils/sdl_compat.h"
 #include "utils/sdl_geometry.h"
 #include "utils/sdl_wrap.h"
+#include "utils/str_cat.hpp"
 #include "utils/stubs.h"
 #include "utils/utf8.hpp"
 
@@ -547,7 +546,7 @@ void LoadHeros()
 
 	for (size_t i = 0; i <= enum_size<HeroClass>::value; ++i) {
 		char portraitPath[18];
-		*fmt::format_to(portraitPath, FMT_COMPILE("ui_art\\hero{}.pcx"), i) = '\0';
+		*BufCopy(portraitPath, "ui_art\\hero", i, ".pcx") = '\0';
 
 		SDL_RWops *handle = OpenAsset(portraitPath);
 		if (handle == nullptr) {
diff --git a/Source/diablo.cpp b/Source/diablo.cpp
index 95c145cf2..088090bee 100644
--- a/Source/diablo.cpp
+++ b/Source/diablo.cpp
@@ -79,6 +79,7 @@
 #include "utils/language.h"
 #include "utils/paths.h"
 #include "utils/stdcompat/string_view.hpp"
+#include "utils/str_cat.hpp"
 #include "utils/utf8.hpp"
 
 #ifdef __vita__
@@ -967,8 +968,8 @@ void DiabloInitScreen()
 
 void SetApplicationVersions()
 {
-	*fmt::format_to_n(gszProductName, sizeof(gszProductName) - 1, "{} v{}", PROJECT_NAME, PROJECT_VERSION).out = '\0';
-	CopyUtf8(gszVersionNumber, fmt::format(fmt::runtime(_("version {:s}")), PROJECT_VERSION), sizeof(gszVersionNumber));
+	*BufCopy(gszProductName, PROJECT_NAME, " v", PROJECT_VERSION) = '\0';
+	*BufCopy(gszVersionNumber, "version ", PROJECT_VERSION) = '\0';
 }
 
 void DiabloInit()
diff --git a/Source/discord/discord.cpp b/Source/discord/discord.cpp
index cffb3b85a..da146e9aa 100644
--- a/Source/discord/discord.cpp
+++ b/Source/discord/discord.cpp
@@ -110,13 +110,14 @@ std::string GetTooltipString()
 
 std::string GetPlayerAssetString()
 {
-	char heroChar = CharChar[static_cast<int>(MyPlayer->_pClass)];
-	char armourChar = ArmourChar[tracked_data.playerGfx >> 4];
-	char wpnChar = WepChar[tracked_data.playerGfx & 0xF];
-
-	std::string result = fmt::format("{}{}{}as", heroChar, armourChar, wpnChar);
-	std::transform(std::begin(result), std::end(result), std::begin(result), [](char c) { return static_cast<char>(std::tolower(c)); });
-	return result;
+	char chars[5] {
+		CharChar[static_cast<int>(MyPlayer->_pClass)] - ('a' - 'A'),
+		ArmourChar[tracked_data.playerGfx >> 4] - ('a' - 'A'),
+		WepChar[tracked_data.playerGfx & 0xF] - ('a' - 'A'),
+		'a',
+		's'
+	};
+	return std::string(chars, 5);
 }
 
 void ResetStartTime()
diff --git a/Source/engine/demomode.cpp b/Source/engine/demomode.cpp
index 1a769da8d..b5f0abb82 100644
--- a/Source/engine/demomode.cpp
+++ b/Source/engine/demomode.cpp
@@ -12,6 +12,7 @@
 #include "pfile.h"
 #include "utils/display.h"
 #include "utils/paths.h"
+#include "utils/str_cat.hpp"
 
 namespace devilution {
 
@@ -75,9 +76,7 @@ void WriteToDemo(T value)
 bool LoadDemoMessages(int i)
 {
 	std::ifstream demofile;
-	char demoFilename[16];
-	*fmt::format_to_n(demoFilename, 15, "demo_{}.dmo", i).out = '\0';
-	demofile.open(paths::PrefPath() + demoFilename, std::fstream::binary);
+	demofile.open(StrCat(paths::PrefPath(), "demo_", i, ".dmo"), std::fstream::binary);
 	if (!demofile.is_open()) {
 		return false;
 	}
@@ -269,9 +268,7 @@ void RecordMessage(tagMSG *lpMsg)
 void NotifyGameLoopStart()
 {
 	if (IsRecording()) {
-		char demoFilename[16];
-		*fmt::format_to_n(demoFilename, 15, "demo_{}.dmo", RecordNumber).out = '\0';
-		DemoRecording.open(paths::PrefPath() + demoFilename, std::fstream::trunc | std::fstream::binary);
+		DemoRecording.open(StrCat(paths::PrefPath(), "demo_", RecordNumber, ".dmo"), std::fstream::trunc | std::fstream::binary);
 		constexpr uint8_t version = 0;
 		WriteToDemo<uint8_t>(version);
 		WriteToDemo<uint32_t>(gSaveNumber);
diff --git a/Source/mpq/mpq_writer.cpp b/Source/mpq/mpq_writer.cpp
index d4feb19e6..1d5262371 100644
--- a/Source/mpq/mpq_writer.cpp
+++ b/Source/mpq/mpq_writer.cpp
@@ -6,8 +6,6 @@
 #include <memory>
 #include <type_traits>
 
-#include <fmt/core.h>
-
 #include "appfat.h"
 #include "encrypt.h"
 #include "engine.h"
@@ -160,7 +158,7 @@ MpqWriter::MpqWriter(const char *path)
 	}
 	return;
 on_error:
-	app_fatal(fmt::format("{}\n{}\n{}", _("Failed to open archive for writing."), path, error));
+	app_fatal(StrCat(_("Failed to open archive for writing."), "\n", path, "\n", error));
 }
 
 MpqWriter::~MpqWriter()