diff --git a/embassy-stm32/src/rcc/l4l5.rs b/embassy-stm32/src/rcc/l4l5.rs
index a10169d6..683b47c0 100644
--- a/embassy-stm32/src/rcc/l4l5.rs
+++ b/embassy-stm32/src/rcc/l4l5.rs
@@ -241,6 +241,7 @@ pub(crate) unsafe fn init(config: Config) {
         w.set_ppre1(config.apb1_pre);
         w.set_ppre2(config.apb2_pre);
     });
+    while RCC.cfgr().read().sws() != config.mux {}
 
     let ahb_freq = sys_clk / config.ahb_pre;