diff --git a/src/mgos_sht31.c b/src/mgos_sht31.c
index b2e8743..83be65b 100644
--- a/src/mgos_sht31.c
+++ b/src/mgos_sht31.c
@@ -48,11 +48,28 @@ static uint8_t crc8(const uint8_t *data, int len)
   }
   return crc;
 }
+
+static uint16_t mgos_sht31_status(struct mgos_sht31 *sensor) {
+  uint8_t data[3];
+  uint16_t value;
+
+  mgos_sht31_cmd(sensor, MGOS_SHT31_READSTATUS);
+  if (!mgos_i2c_read(sensor->i2c, sensor->i2caddr, data, 3, true))
+    return 0;
+
+  // Check CRC8 checksums
+  if ((data[2]!=crc8(data, 2)))
+    return 0;
+  value=(data[0]<<8) + data[1];
+
+  return value;
+}
 // Private functions end
 
 // Public functions follow
 struct mgos_sht31 *mgos_sht31_create(struct mgos_i2c *i2c, uint8_t i2caddr) {
   struct mgos_sht31 *sensor;
+  uint16_t status0, status1, status2;
 
   if (!i2c) return NULL;
 
@@ -63,7 +80,21 @@ struct mgos_sht31 *mgos_sht31_create(struct mgos_i2c *i2c, uint8_t i2caddr) {
   sensor->last_read_time=0;
 
   mgos_sht31_cmd(sensor, MGOS_SHT31_SOFTRESET);
-  return sensor;
+
+  // Toggle heater on and off, which shows up in status register bit 13 (0=Off, 1=On)
+  status0=mgos_sht31_status(sensor); // heater is off, bit13 is 0
+  mgos_sht31_cmd(sensor, MGOS_SHT31_HEATEREN);
+  status1=mgos_sht31_status(sensor); // heater is on, bit13 is 1
+  mgos_sht31_cmd(sensor, MGOS_SHT31_HEATERDIS);
+  status2=mgos_sht31_status(sensor); // heater is off, bit13 is 0
+
+  if (((status0 & 0x2000) == 0) && ((status1 & 0x2000) != 0) && ((status2 & 0x2000) == 0)) {
+    LOG(LL_INFO, ("SHT31 created at I2C 0x%02x", i2caddr));
+    return sensor;
+  }
+
+  free(sensor);
+  return NULL;
 }
 
 void mgos_sht31_destroy(struct mgos_sht31 **sensor) {
diff --git a/src/mgos_si7021.c b/src/mgos_si7021.c
index 5117482..1781fa1 100644
--- a/src/mgos_si7021.c
+++ b/src/mgos_si7021.c
@@ -60,7 +60,6 @@ struct mgos_si7021 *mgos_si7021_create(struct mgos_i2c *i2c, uint8_t i2caddr) {
     LOG(LL_ERROR, ("Chip ID register invalid, expected 0x3A got 0x%02x (%d)", ret, ret));
     return NULL;
   }
-  LOG(LL_INFO, ("SI7021 found at I2C 0x%02x", i2caddr));
 
   sensor=calloc(1, sizeof(struct mgos_si7021));
   if (!sensor) return NULL;
@@ -68,6 +67,7 @@ struct mgos_si7021 *mgos_si7021_create(struct mgos_i2c *i2c, uint8_t i2caddr) {
   sensor->i2c=i2c;
   sensor->last_read_time=0;
 
+  LOG(LL_INFO, ("SI7021 created at I2C 0x%02x", i2caddr));
   return sensor;
 }