diff --git a/stmhal/rtc.c b/stmhal/rtc.c
index 679f5866315feb3a28339d5d57e30187ff377b91..6bed3d1e62bac5bd024ae42564b9bfb20d7748d7 100644
--- a/stmhal/rtc.c
+++ b/stmhal/rtc.c
@@ -507,34 +507,34 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_rtc_wakeup_obj, 2, 4, pyb_rtc_wakeup);
 mp_obj_t pyb_rtc_calibration(mp_uint_t n_args, const mp_obj_t *args) {
     mp_int_t cal;
     if (n_args == 2) {
-	cal = mp_obj_get_int(args[1]);
-	mp_uint_t cal_p, cal_m;
-	if (cal < -511 || cal > 512) {
-	    nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError,
-					       "calibration value out of range"));
-	}
-	if (cal > 0) {
-	    cal_p = RTC_SMOOTHCALIB_PLUSPULSES_SET;
-	    cal_m = 512 - cal;
-	} else {
-	    cal_p = RTC_SMOOTHCALIB_PLUSPULSES_RESET;
-	    cal_m = -cal;
-	}
-	HAL_RTCEx_SetSmoothCalib(&RTCHandle, RTC_SMOOTHCALIB_PERIOD_32SEC, cal_p, cal_m);
-	return mp_const_none;
+        cal = mp_obj_get_int(args[1]);
+        mp_uint_t cal_p, cal_m;
+        if (cal < -511 || cal > 512) {
+            nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError,
+                "calibration value out of range"));
+        }
+        if (cal > 0) {
+            cal_p = RTC_SMOOTHCALIB_PLUSPULSES_SET;
+            cal_m = 512 - cal;
+        } else {
+            cal_p = RTC_SMOOTHCALIB_PLUSPULSES_RESET;
+            cal_m = -cal;
+        }
+        HAL_RTCEx_SetSmoothCalib(&RTCHandle, RTC_SMOOTHCALIB_PERIOD_32SEC, cal_p, cal_m);
+        return mp_const_none;
     } else {
         // printf("CALR = 0x%x\n", (mp_uint_t) RTCHandle.Instance->CALR); // DEBUG
-	// Test if CALP bit is set in CALR:
-	if (RTCHandle.Instance->CALR & 0x8000) {
-	    cal = 512 - (RTCHandle.Instance->CALR & 0x1ff);
-	} else {
-	    cal = -(RTCHandle.Instance->CALR & 0x1ff);
-	}
-	return mp_obj_new_int(cal);
+        // Test if CALP bit is set in CALR:
+        if (RTCHandle.Instance->CALR & 0x8000) {
+            cal = 512 - (RTCHandle.Instance->CALR & 0x1ff);
+        } else {
+            cal = -(RTCHandle.Instance->CALR & 0x1ff);
+        }
+        return mp_obj_new_int(cal);
     }
 }
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_rtc_calibration_obj, 1, 2, pyb_rtc_calibration);
-    
+
 STATIC const mp_map_elem_t pyb_rtc_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_info), (mp_obj_t)&pyb_rtc_info_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_datetime), (mp_obj_t)&pyb_rtc_datetime_obj },