diff --git a/cpu/samd5x/cpu.c b/cpu/samd5x/cpu.c
index 54555b2dc1..734123dbeb 100644
--- a/cpu/samd5x/cpu.c
+++ b/cpu/samd5x/cpu.c
@@ -203,4 +203,9 @@ void cpu_init(void)
 
     /* trigger static peripheral initialization */
     periph_init();
+
+    /* set ONDEMAND bit after all clocks have been configured */
+    /* This is to avoid setting the source for the main clock to ONDEMAND before using it. */
+    OSCCTRL->DFLLCTRLA.reg |= OSCCTRL_DFLLCTRLA_ONDEMAND;
+    OSCCTRL->Dpll[0].DPLLCTRLA.reg |= OSCCTRL_DPLLCTRLA_ONDEMAND;
 }