diff --git a/rpcs3/Emu/Cell/lv2/sys_prx.cpp b/rpcs3/Emu/Cell/lv2/sys_prx.cpp
index 44980dc627..76e206fbbb 100644
--- a/rpcs3/Emu/Cell/lv2/sys_prx.cpp
+++ b/rpcs3/Emu/Cell/lv2/sys_prx.cpp
@@ -236,10 +236,9 @@ error_code _sys_prx_start_module(u32 id, u64 flags, vm::ptr<sys_prx_start_stop_m
 		return CELL_ESRCH;
 	}
 
-	//if (prx->is_started)
-	//	return CELL_PRX_ERROR_ALREADY_STARTED;
+	if (prx->is_started.exchange(true))
+		return not_an_error(CELL_PRX_ERROR_ALREADY_STARTED);
 
-	//prx->is_started = true;
 	pOpt->entry.set(prx->start ? prx->start.addr() : ~0ull);
 	pOpt->entry2.set(prx->prologue ? prx->prologue.addr() : ~0ull);
 	return CELL_OK;
@@ -256,10 +255,9 @@ error_code _sys_prx_stop_module(u32 id, u64 flags, vm::ptr<sys_prx_start_stop_mo
 		return CELL_ESRCH;
 	}
 
-	//if (!prx->is_started)
-	//	return CELL_PRX_ERROR_ALREADY_STOPPED;
+	if (!prx->is_started.exchange(false))
+		return not_an_error(CELL_PRX_ERROR_ALREADY_STOPPED);
 
-	//prx->is_started = false;
 	pOpt->entry.set(prx->stop ? prx->stop.addr() : ~0ull);
 	pOpt->entry2.set(prx->epilogue ? prx->epilogue.addr() : ~0ull);
 
diff --git a/rpcs3/Emu/Cell/lv2/sys_prx.h b/rpcs3/Emu/Cell/lv2/sys_prx.h
index 26643b517d..ffc967e604 100644
--- a/rpcs3/Emu/Cell/lv2/sys_prx.h
+++ b/rpcs3/Emu/Cell/lv2/sys_prx.h
@@ -119,7 +119,7 @@ struct lv2_prx final : lv2_obj, ppu_module
 {
 	static const u32 id_base = 0x23000000;
 
-	bool is_started = false;
+	atomic_t<bool> is_started = false;
 
 	std::unordered_map<u32, u32> specials;
 	std::unordered_map<u32, void*> imports;