diff --git a/sonoff/_releasenotes.ino b/sonoff/_releasenotes.ino
index d6b3ae0e5..c228c4e6d 100644
--- a/sonoff/_releasenotes.ino
+++ b/sonoff/_releasenotes.ino
@@ -1,4 +1,7 @@
-/* 5.12.0b
+/* 5.12.0c
+ * Fix intermittent exception when dns lookup is used while sleep is enabled
+ *
+ * 5.12.0b
  * Add serial debug info
  * Add Multichannel Gas sensor using MultiChannel_Gas_Sensor library (#1245)
  * Add optional usage of %d or %X suffices in MQTT client to append chipid (#1871)
@@ -19,7 +22,7 @@
  * 5.12.0a
  * Change platformio option sonoff-ds18x20 to sonoff-xxl enabling ds18x20 and all other sensors in one image
  * Fix providing web page configuratin option for Friendly Name when no device (relay or light) is configured (#1850)
- * Change default paremeters in user_config.h to undefined for easy installation (#1851)
+ * Change default parameters in user_config.h to undefined for easy installation (#1851)
  * Change max user configurable hold time from 10 to 25 seconds (#1851)
  *
  * 5.12.0 20180209
diff --git a/sonoff/sonoff.ino b/sonoff/sonoff.ino
index 1f2a524d9..f0ba58af8 100644
--- a/sonoff/sonoff.ino
+++ b/sonoff/sonoff.ino
@@ -25,7 +25,7 @@
     - Select IDE Tools - Flash Size: "1M (no SPIFFS)"
   ====================================================*/
 
-#define VERSION                0x050C0002   // 5.12.0b
+#define VERSION                0x050C0003   // 5.12.0c
 
 // Location specific includes
 #include <core_version.h>                   // Arduino_Esp8266 version information (ARDUINO_ESP8266_RELEASE and ARDUINO_ESP8266_RELEASE_2_3_0)
diff --git a/sonoff/support.ino b/sonoff/support.ino
index a086f1207..f8c706a31 100644
--- a/sonoff/support.ino
+++ b/sonoff/support.ino
@@ -17,8 +17,8 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-IPAddress syslog_host_addr;  // Syslog host IP address
-unsigned long syslog_host_refresh = 0;
+IPAddress syslog_host_addr;      // Syslog host IP address
+uint32_t syslog_host_hash = 0;   // Syslog host name hash
 
 /*********************************************************************************************\
  * Watchdog extension (https://github.com/esp8266/Arduino/issues/1532)
@@ -414,6 +414,15 @@ void SetSerialBaudrate(int baudrate)
   }
 }
 
+uint32_t GetHash(const char *buffer, size_t size)
+{
+  uint32_t hash = 0;
+  for (uint16_t i = 0; i <= size; i++) {
+    hash += (uint8_t)*buffer++ * (i +1);
+  }
+  return hash;
+}
+
 /*********************************************************************************************\
  * Wifi
 \*********************************************************************************************/
@@ -1245,7 +1254,7 @@ void RtcSecond()
   uint32_t dstoffset;
   TIME_T tmpTime;
 
-  if ((ntp_sync_minute > 59) && (3 == RtcTime.minute)) ntp_sync_minute = 1;                // If sync prepare for a new cycle
+  if ((ntp_sync_minute > 59) && (RtcTime.minute > 2)) ntp_sync_minute = 1;                 // If sync prepare for a new cycle
   uint8_t offset = (uptime < 30) ? RtcTime.second : (((ESP.getChipId() & 0xF) * 3) + 3) ;  // First try ASAP to sync. If fails try once every 60 seconds based on chip id
   if ((WL_CONNECTED == WiFi.status()) && (offset == RtcTime.second) && ((RtcTime.year < 2016) || (ntp_sync_minute == RtcTime.minute))) {
     ntp_time = sntp_get_current_timestamp();
@@ -1396,9 +1405,9 @@ void Syslog()
   // Destroys log_data
   char syslog_preamble[64];  // Hostname + Id
 
-  if ((static_cast<uint32_t>(syslog_host_addr) == 0) || ((millis() - syslog_host_refresh) > 60000)) {
-    WiFi.hostByName(Settings.syslog_host, syslog_host_addr);
-    syslog_host_refresh = millis();
+  if (syslog_host_hash != GetHash(Settings.syslog_host, strlen(Settings.syslog_host))) {
+    syslog_host_hash = GetHash(Settings.syslog_host, strlen(Settings.syslog_host));
+    WiFi.hostByName(Settings.syslog_host, syslog_host_addr);  // If sleep enabled this might result in exception so try to do it once using hash
   }
   if (PortUdp.beginPacket(syslog_host_addr, Settings.syslog_port)) {
     snprintf_P(syslog_preamble, sizeof(syslog_preamble), PSTR("%s ESP-"), my_hostname);