diff --git a/core/hw/naomi/multiboard.cpp b/core/hw/naomi/multiboard.cpp
index 9ce8f9cfd..344f1cb01 100644
--- a/core/hw/naomi/multiboard.cpp
+++ b/core/hw/naomi/multiboard.cpp
@@ -127,6 +127,11 @@ void Multiboard::startSlave()
 	int x = cfgLoadInt("window", "left", (1920 - 640) / 2);
 	int y = cfgLoadInt("window", "top", (1080 - 480) / 2);
 	int width = cfgLoadInt("window", "width", 640);
+	std::string biosFile = CurrentCartridge->game->bios == nullptr ? "naomi" : CurrentCartridge->game->bios;
+	std::string biosPath = hostfs::findNaomiBios(biosFile + ".zip");
+	if (biosPath.empty())
+		biosPath = hostfs::findNaomiBios(biosFile + ".7z");
+
 	for (int i = 0; i < slaves; i++)
 	{
 		std::string region = "config:Dreamcast.Region=" + std::to_string(config::Region);
@@ -143,7 +148,7 @@ void Multiboard::startSlave()
 			"-config", region.c_str(),
 			"-config", left.c_str(),
 			"-config", top.c_str(),
-			CurrentCartridge->game->bios == nullptr ? "naomi" : CurrentCartridge->game->bios
+			biosPath.c_str()
 		};
 		os_RunInstance(std::size(args), args);
 	}
diff --git a/core/hw/naomi/naomi_cart.cpp b/core/hw/naomi/naomi_cart.cpp
index 24ec3a441..2cc79cb43 100644
--- a/core/hw/naomi/naomi_cart.cpp
+++ b/core/hw/naomi/naomi_cart.cpp
@@ -56,22 +56,40 @@ bool atomiswaveForceFeedback;
 
 static bool loadBios(const char *filename, Archive *child_archive, Archive *parent_archive, int region)
 {
+	std::string path;
+	std::string biosName;
+	if (settings.naomi.slave)
+	{
+		// extract basename of bios
+		biosName = get_file_basename(filename);
+		size_t idx = get_last_slash_pos(biosName);
+		if (idx != std::string::npos)
+			biosName = biosName.substr(idx + 1);
+		path = filename;
+	}
+	else
+	{
+		biosName = filename;
+	}
 	int biosid = 0;
 	for (; BIOS[biosid].name != nullptr; biosid++)
-		if (!stricmp(BIOS[biosid].name, filename))
+		if (!stricmp(BIOS[biosid].name, biosName.c_str()))
 			break;
 	if (BIOS[biosid].name == nullptr)
 	{
-		WARN_LOG(NAOMI, "Unknown BIOS %s", filename);
+		WARN_LOG(NAOMI, "Unknown BIOS %s", biosName.c_str());
 		return false;
 	}
 
 	const BIOS_t *bios = &BIOS[biosid];
 
-	std::string arch_name(bios->filename != nullptr ? bios->filename : filename);
-	std::string path = hostfs::findNaomiBios(arch_name + ".zip");
 	if (path.empty())
-		path = hostfs::findNaomiBios(arch_name + ".7z");
+	{
+		std::string arch_name(bios->filename != nullptr ? bios->filename : filename);
+		path = hostfs::findNaomiBios(arch_name + ".zip");
+		if (path.empty())
+			path = hostfs::findNaomiBios(arch_name + ".7z");
+	}
 	DEBUG_LOG(NAOMI, "Loading BIOS from %s", path.c_str());
 	std::unique_ptr<Archive> bios_archive(OpenArchive(path));