diff --git a/sonoff/_changelog.ino b/sonoff/_changelog.ino
index d53687938..0750b4d06 100644
--- a/sonoff/_changelog.ino
+++ b/sonoff/_changelog.ino
@@ -1,5 +1,6 @@
 /* 6.3.0.3 20181105
  * Fix hardware serial pin configuration. To keep using hardware serial swap current Rx/Tx pin configuration only (#4280)
+ * Add more strict checks for GPIO selections
  *
  * 6.3.0.2 20181101
  * Add minutes to commands Timezone to allow all possible world timezones
diff --git a/sonoff/sonoff.ino b/sonoff/sonoff.ino
index 7a3948382..09e029a15 100755
--- a/sonoff/sonoff.ino
+++ b/sonoff/sonoff.ino
@@ -869,13 +869,20 @@ void MqttDataHandler(char* topic, byte* data, unsigned int data_len)
       mytmplt cmodule;
       memcpy_P(&cmodule, &kModules[Settings.module], sizeof(cmodule));
       if ((GPIO_USER == ValidGPIO(index, cmodule.gp.io[index])) && (payload >= 0) && (payload < GPIO_SENSOR_END)) {
-        for (byte i = 0; i < MAX_GPIO_PIN; i++) {
-          if ((GPIO_USER == ValidGPIO(i, cmodule.gp.io[i])) && (Settings.my_gp.io[i] == payload)) {
-            Settings.my_gp.io[i] = 0;
-          }
+        bool present = false;
+        for (byte i = 0; i < sizeof(kGpioNiceList); i++) {
+          uint8_t midx = pgm_read_byte(kGpioNiceList + i);
+          if (midx == payload) { present = true; }
+        }
+        if (present) {
+          for (byte i = 0; i < MAX_GPIO_PIN; i++) {
+            if ((GPIO_USER == ValidGPIO(i, cmodule.gp.io[i])) && (Settings.my_gp.io[i] == payload)) {
+              Settings.my_gp.io[i] = 0;
+            }
+          }
+          Settings.my_gp.io[index] = payload;
+          restart_flag = 2;
         }
-        Settings.my_gp.io[index] = payload;
-        restart_flag = 2;
       }
       snprintf_P(mqtt_data, sizeof(mqtt_data), PSTR("{"));
       for (byte i = 0; i < MAX_GPIO_PIN; i++) {
@@ -895,16 +902,19 @@ void MqttDataHandler(char* topic, byte* data, unsigned int data_len)
     else if (CMND_GPIOS == command_code) {
       mytmplt cmodule;
       memcpy_P(&cmodule, &kModules[Settings.module], sizeof(cmodule));
-      for (byte i = 0; i < GPIO_SENSOR_END; i++) {
-        if (!GetUsedInModule(i, cmodule.gp.io)) {
+      uint8_t midx;
+      for (byte i = 0; i < sizeof(kGpioNiceList); i++) {
+        midx = pgm_read_byte(kGpioNiceList + i);
+        if (!GetUsedInModule(midx, cmodule.gp.io)) {
+
           if (!jsflg) {
             snprintf_P(mqtt_data, sizeof(mqtt_data), PSTR("{\"" D_CMND_GPIOS "%d\":["), lines);
           } else {
             snprintf_P(mqtt_data, sizeof(mqtt_data), PSTR("%s,"), mqtt_data);
           }
           jsflg = 1;
-          snprintf_P(mqtt_data, sizeof(mqtt_data), PSTR("%s\"%d (%s)\""), mqtt_data, i, GetTextIndexed(stemp1, sizeof(stemp1), i, kSensorNames));
-          if ((strlen(mqtt_data) > (LOGSZ - TOPSZ)) || (i == GPIO_SENSOR_END -1)) {
+          snprintf_P(mqtt_data, sizeof(mqtt_data), PSTR("%s\"%d (%s)\""), mqtt_data, midx, GetTextIndexed(stemp1, sizeof(stemp1), midx, kSensorNames));
+          if ((strlen(mqtt_data) > (LOGSZ - TOPSZ)) || (i == sizeof(kGpioNiceList) -1)) {
             snprintf_P(mqtt_data, sizeof(mqtt_data), PSTR("%s]}"), mqtt_data);
             MqttPublishPrefixTopic_P(RESULT_OR_STAT, type);
             jsflg = 0;
@@ -912,6 +922,7 @@ void MqttDataHandler(char* topic, byte* data, unsigned int data_len)
           }
         }
       }
+
       mqtt_data[0] = '\0';
     }
     else if ((CMND_PWM == command_code) && pwm_present && (index > 0) && (index <= MAX_PWMS)) {
diff --git a/sonoff/sonoff_template.h b/sonoff/sonoff_template.h
index 036e2400d..eb4d910d0 100644
--- a/sonoff/sonoff_template.h
+++ b/sonoff/sonoff_template.h
@@ -267,7 +267,7 @@ typedef struct MYTMPLT {
   myio         gp;
 } mytmplt;
 
-const uint8_t kGpioNiceList[GPIO_SENSOR_END] PROGMEM = {
+const uint8_t kGpioNiceList[] PROGMEM = {
   GPIO_NONE,           // Not used
   GPIO_KEY1,           // Buttons
   GPIO_KEY1_NP,
@@ -335,48 +335,96 @@ const uint8_t kGpioNiceList[GPIO_SENSOR_END] PROGMEM = {
   GPIO_CNTR3_NP,
   GPIO_CNTR4,
   GPIO_CNTR4_NP,
+#ifdef USE_I2C
   GPIO_I2C_SCL,        // I2C SCL
   GPIO_I2C_SDA,        // I2C SDA
+#endif
+#ifdef USE_SPI
   GPIO_SPI_CS,         // SPI Chip Select
   GPIO_SPI_DC,         // SPI Data Direction
+#endif
+#ifdef USE_DISPLAY
   GPIO_BACKLIGHT,      // Display backlight control
+#endif
   GPIO_DHT11,          // DHT11
   GPIO_DHT22,          // DHT21, DHT22, AM2301, AM2302, AM2321
   GPIO_SI7021,         // iTead SI7021
   GPIO_DSB,            // Single wire DS18B20 or DS18S20
+#ifdef USE_WS2812
   GPIO_WS2812,         // WS2812 Led string
+#endif
+#ifdef USE_IR_REMOTE
   GPIO_IRSEND,         // IR remote
+#ifdef USE_IR_RECEIVE
   GPIO_IRRECV,         // IR receiver
+#endif
+#endif
+#ifdef USE_RC_SWITCH
   GPIO_RFSEND,         // RF transmitter
   GPIO_RFRECV,         // RF receiver
+#endif
+#ifdef USE_SR04
   GPIO_SR04_TRIG,      // SR04 Trigger pin
   GPIO_SR04_ECHO,      // SR04 Echo pin
+#endif
+#ifdef USE_TM1638
   GPIO_TM16CLK,        // TM1638 Clock
   GPIO_TM16DIO,        // TM1638 Data I/O
   GPIO_TM16STB,        // TM1638 Strobe
+#endif
+#ifdef USE_HX711
   GPIO_HX711_SCK,      // HX711 Load Cell clock
   GPIO_HX711_DAT,      // HX711 Load Cell data
+#endif
+#ifdef USE_SERIAL_BRIDGE
   GPIO_SBR_TX,         // Serial Bridge Serial interface
   GPIO_SBR_RX,         // Serial Bridge Serial interface
+#endif
+#ifdef USE_MHZ19
   GPIO_MHZ_TXD,        // MH-Z19 Serial interface
   GPIO_MHZ_RXD,        // MH-Z19 Serial interface
+#endif
+#ifdef USE_SENSEAIR
   GPIO_SAIR_TX,        // SenseAir Serial interface
   GPIO_SAIR_RX,        // SenseAir Serial interface
+#endif
+#ifdef USE_NOVA_SDS
   GPIO_SDS0X1_TX,      // Nova Fitness SDS011 Serial interface
   GPIO_SDS0X1_RX,      // Nova Fitness SDS011 Serial interface
+#endif
+#if defined(USE_PZEM004T) || defined(USE_PZEM_AC) || defined(USE_PZEM_DC)
   GPIO_PZEM0XX_TX,     // PZEM0XX Serial interface
+#endif
+#ifdef USE_PZEM004T
   GPIO_PZEM004_RX,     // PZEM004T Serial interface
+#endif
+#ifdef USE_PZEM_AC
   GPIO_PZEM016_RX,     // PZEM-014,016 Serial Modbus interface
+#endif
+#ifdef USE_PZEM_DC
   GPIO_PZEM017_RX,     // PZEM-003,017 Serial Modbus interface
+#endif
+#ifdef USE_SDM120
   GPIO_SDM120_TX,      // SDM120 Serial interface
   GPIO_SDM120_RX,      // SDM120 Serial interface
+#endif
+#ifdef USE_SDM630
   GPIO_SDM630_TX,      // SDM630 Serial interface
   GPIO_SDM630_RX,      // SDM630 Serial interface
+#endif
+#ifdef USE_PMS5003
   GPIO_PMS5003,        // Plantower PMS5003 Serial interface
+#endif
+#ifdef USE_TX20_WIND_SENSOR
   GPIO_TX20_TXD_BLACK, // TX20 Transmission Pin
+#endif
+#ifdef USE_MP3_PLAYER
   GPIO_MP3_DFR562,     // RB-DFR-562, DFPlayer Mini MP3 Player Serial interface
+#endif
+#ifdef USE_TUYA_DIMMER
   GPIO_TUYA_TX,        // Tuya Serial interface
   GPIO_TUYA_RX         // Tuya Serial interface
+#endif
 };
 
 const uint8_t kModuleNiceList[MAXMODULE] PROGMEM = {
diff --git a/sonoff/support.ino b/sonoff/support.ino
index ba7ae0d6e..c2856a782 100644
--- a/sonoff/support.ino
+++ b/sonoff/support.ino
@@ -646,89 +646,20 @@ boolean GetUsedInModule(byte val, uint8_t *arr)
   int offset = 0;
 
   if (!val) { return false; }  // None
-#ifndef USE_I2C
-  if (GPIO_I2C_SCL == val) { return true; }
-  if (GPIO_I2C_SDA == val) { return true; }
-#endif
-#ifndef USE_WS2812
-  if (GPIO_WS2812 == val) { return true; }
-#endif
-#ifndef USE_IR_REMOTE
-  if (GPIO_IRSEND == val) { return true; }
-#ifndef USE_IR_RECEIVE
-  if (GPIO_IRRECV == val) { return true; }
-#endif
-#endif
-#ifndef USE_MHZ19
-  if (GPIO_MHZ_TXD == val) { return true; }
-  if (GPIO_MHZ_RXD == val) { return true; }
-#endif
 
-  int pzem = 3;
-#ifndef USE_PZEM004T
-  pzem--;
-  if (GPIO_PZEM004_RX == val) { return true; }
-#endif
-#ifndef USE_PZEM_AC
-  pzem--;
-  if (GPIO_PZEM016_RX == val) { return true; }
-#endif
-#ifndef USE_PZEM_DC
-  pzem--;
-  if (GPIO_PZEM017_RX == val) { return true; }
-#endif
-  if (!pzem && (GPIO_PZEM0XX_TX == val)) { return true; }
+  if ((val >= GPIO_KEY1) && (val < GPIO_KEY1 + MAX_KEYS)) {
+    offset = (GPIO_KEY1_NP - GPIO_KEY1);
+  }
+  if ((val >= GPIO_KEY1_NP) && (val < GPIO_KEY1_NP + MAX_KEYS)) {
+    offset = -(GPIO_KEY1_NP - GPIO_KEY1);
+  }
 
-#ifndef USE_SENSEAIR
-  if (GPIO_SAIR_TX == val) { return true; }
-  if (GPIO_SAIR_RX == val) { return true; }
-#endif
-#ifndef USE_SPI
-  if (GPIO_SPI_CS == val) { return true; }
-  if (GPIO_SPI_DC == val) { return true; }
-#endif
-#ifndef USE_DISPLAY
-  if (GPIO_BACKLIGHT == val) { return true; }
-#endif
-#ifndef USE_PMS5003
-  if (GPIO_PMS5003 == val) { return true; }
-#endif
-#ifndef USE_NOVA_SDS
-  if (GPIO_SDS0X1_TX == val) { return true; }
-  if (GPIO_SDS0X1_RX == val) { return true; }
-#endif
-#ifndef USE_SERIAL_BRIDGE
-  if (GPIO_SBR_TX == val) { return true; }
-  if (GPIO_SBR_RX == val) { return true; }
-#endif
-#ifndef USE_SR04
-  if (GPIO_SR04_TRIG == val) { return true; }
-  if (GPIO_SR04_ECHO == val) { return true; }
-#endif
-#ifndef USE_SDM120
-  if (GPIO_SDM120_TX == val) { return true; }
-  if (GPIO_SDM120_RX == val) { return true; }
-#endif
-#ifndef USE_SDM630
-  if (GPIO_SDM630_TX == val) { return true; }
-  if (GPIO_SDM630_RX == val) { return true; }
-#endif
-#ifndef USE_TM1638
-  if (GPIO_TM16CLK == val) { return true; }
-  if (GPIO_TM16DIO == val) { return true; }
-  if (GPIO_TM16STB == val) { return true; }
-#endif
-#ifndef USE_HX711
-  if (GPIO_HX711_SCK == val) { return true; }
-  if (GPIO_HX711_DAT == val) { return true; }
-#endif
-#ifndef USE_TX20_WIND_SENSOR
-  if (GPIO_TX20_TXD_BLACK == val) { return true; }
-#endif
-#ifndef USE_RC_SWITCH
-  if (GPIO_RFSEND == val) { return true; }
-  if (GPIO_RFRECV == val) { return true; }
-#endif
+  if ((val >= GPIO_SWT1) && (val < GPIO_SWT1 + MAX_SWITCHES)) {
+    offset = (GPIO_SWT1_NP - GPIO_SWT1);
+  }
+  if ((val >= GPIO_SWT1_NP) && (val < GPIO_SWT1_NP + MAX_SWITCHES)) {
+    offset = -(GPIO_SWT1_NP - GPIO_SWT1);
+  }
 
   if ((val >= GPIO_REL1) && (val < GPIO_REL1 + MAX_RELAYS)) {
     offset = (GPIO_REL1_INV - GPIO_REL1);
@@ -750,6 +681,14 @@ boolean GetUsedInModule(byte val, uint8_t *arr)
   if ((val >= GPIO_PWM1_INV) && (val < GPIO_PWM1_INV + MAX_PWMS)) {
     offset = -(GPIO_PWM1_INV - GPIO_PWM1);
   }
+
+  if ((val >= GPIO_CNTR1) && (val < GPIO_CNTR1 + MAX_COUNTERS)) {
+    offset = (GPIO_CNTR1_NP - GPIO_CNTR1);
+  }
+  if ((val >= GPIO_CNTR1_NP) && (val < GPIO_CNTR1_NP + MAX_COUNTERS)) {
+    offset = -(GPIO_CNTR1_NP - GPIO_CNTR1);
+  }
+
   for (byte i = 0; i < MAX_GPIO_PIN; i++) {
     if (arr[i] == val) { return true; }
     if (arr[i] == val + offset) { return true; }
diff --git a/sonoff/xdrv_01_webserver.ino b/sonoff/xdrv_01_webserver.ino
index 8f7bcdefb..e7327b769 100644
--- a/sonoff/xdrv_01_webserver.ino
+++ b/sonoff/xdrv_01_webserver.ino
@@ -773,7 +773,7 @@ void HandleModuleConfiguration()
 
   mytmplt cmodule;
   memcpy_P(&cmodule, &kModules[Settings.module], sizeof(cmodule));
-  for (byte j = 0; j < GPIO_SENSOR_END; j++) {
+  for (byte j = 0; j < sizeof(kGpioNiceList); j++) {
     midx = pgm_read_byte(kGpioNiceList + j);
     if (!GetUsedInModule(midx, cmodule.gp.io)) {
       snprintf_P(mqtt_data, sizeof(mqtt_data), HTTP_SCRIPT_MODULE2, midx, midx, GetTextIndexed(stemp, sizeof(stemp), midx, kSensorNames));