diff --git a/lib/stm32/f2/rcc.c b/lib/stm32/f2/rcc.c
index b662cebb..d01dbcc0 100644
--- a/lib/stm32/f2/rcc.c
+++ b/lib/stm32/f2/rcc.c
@@ -355,6 +355,10 @@ void rcc_clock_setup_hse_3v3(const struct rcc_clock_scale *clock)
 	rcc_set_ppre1(clock->ppre1);
 	rcc_set_ppre2(clock->ppre2);
 
+	/* Disable PLL oscillator before changing its configuration. */
+	rcc_osc_off(RCC_PLL);
+
+	/* Configure the PLL oscillator. */
 	rcc_set_main_pll_hse(clock->pllm, clock->plln,
 			     clock->pllp, clock->pllq);
 
diff --git a/lib/stm32/f4/rcc.c b/lib/stm32/f4/rcc.c
index 5dd775d5..7e3c0da3 100644
--- a/lib/stm32/f4/rcc.c
+++ b/lib/stm32/f4/rcc.c
@@ -709,6 +709,10 @@ void rcc_clock_setup_hse_3v3(const struct rcc_clock_scale *clock)
 	rcc_set_ppre1(clock->ppre1);
 	rcc_set_ppre2(clock->ppre2);
 
+	/* Disable PLL oscillator before changing its configuration. */
+	rcc_osc_off(RCC_PLL);
+
+	/* Configure the PLL oscillator. */
 	rcc_set_main_pll_hse(clock->pllm, clock->plln,
 			clock->pllp, clock->pllq, clock->pllr);
 
diff --git a/lib/stm32/f7/rcc.c b/lib/stm32/f7/rcc.c
index ea6dcd50..186109a5 100644
--- a/lib/stm32/f7/rcc.c
+++ b/lib/stm32/f7/rcc.c
@@ -392,6 +392,10 @@ void rcc_clock_setup_hse(const struct rcc_clock_scale *clock, uint32_t hse_mhz)
 	rcc_set_ppre1(clock->ppre1);
 	rcc_set_ppre2(clock->ppre2);
 
+	/* Disable PLL oscillator before changing its configuration. */
+	rcc_osc_off(RCC_PLL);
+
+	/* Configure the PLL oscillator. */
 	rcc_set_main_pll_hse(pllm, clock->plln,
 			     clock->pllp, clock->pllq);
 
diff --git a/lib/stm32/l1/rcc.c b/lib/stm32/l1/rcc.c
index e9f7bd68..41cf1999 100644
--- a/lib/stm32/l1/rcc.c
+++ b/lib/stm32/l1/rcc.c
@@ -535,6 +535,10 @@ void rcc_clock_setup_pll(const struct rcc_clock_scale *clock)
 	flash_prefetch_enable();
 	flash_set_ws(clock->flash_waitstates);
 
+	/* Disable PLL oscillator before changing its configuration. */
+	rcc_osc_off(RCC_PLL);
+
+	/* Configure the PLL oscillator. */
 	rcc_set_pll_configuration(clock->pll_source, clock->pll_mul,
 				  clock->pll_div);