diff --git a/targets/TARGET_STM/pwmout_api.c b/targets/TARGET_STM/pwmout_api.c
index dfacdc4f995..53e3d890b9b 100644
--- a/targets/TARGET_STM/pwmout_api.c
+++ b/targets/TARGET_STM/pwmout_api.c
@@ -142,9 +142,23 @@ static void _pwmout_init_direct(pwmout_t *obj, const PinMap *pinmap)
         pin_function(pinmap->pin, pinmap->function);
         pin_mode(pinmap->pin, PullNone);
 
-        obj->period = 0;
-        obj->pulse = 0;
-        obj->prescaler = 0;
+        // Initialize obj with default values (period 550Hz, duty 0%)
+        uint32_t frequency;
+        uint32_t clocksource = __HAL_RCC_GET_HRTIM1_SOURCE();
+        switch (clocksource) {
+            case RCC_HRTIM1CLK_TIMCLK:
+                frequency = HAL_RCC_GetHCLKFreq();
+                break;
+            case RCC_HRTIM1CLK_CPUCLK:
+                frequency = HAL_RCC_GetSysClockFreq();
+                break;
+        }
+        obj->period = 18000 * (frequency / 1000000) / 4;
+        if (obj->period > 0xFFDFU) {
+            obj->period = 0xFFDFU;
+        }
+        obj->pulse = (uint32_t)((float)obj->period * 1.0 + 0.5);
+        obj->prescaler = HRTIM_PRESCALERRATIO_DIV4;
 
         // Initialize the HRTIM structure
         HrtimHandle.Instance = HRTIM1;