diff --git a/sonoff/_changelog.ino b/sonoff/_changelog.ino
index 5b2497eb5..450ef7859 100644
--- a/sonoff/_changelog.ino
+++ b/sonoff/_changelog.ino
@@ -3,6 +3,7 @@
  * Add LED GPIO option "LedLink" (157) and "LedLinki" (158) to select dedicated link status LED (#5709)
  * Add support for up to four LEDs related to four power outputs. Enabled when "LedLink(i)" is configured too (#5709)
  * Add extended LED power control using command LedPowerX where X is 1 to 4. Enabled when "LedLink(i)" is configured too (#5709)
+ * Fix core 2.5.x ISR not in IRAM exception (#5837)
  *
  * 6.5.0.11 20190517
  * Add command SetOption64 0/1 to switch between "-" or "_" as sensor index separator impacting DS18X20, DHT, BMP and SHT3X sensor names (#5689)
diff --git a/sonoff/support_rotary.ino b/sonoff/support_rotary.ino
index c04889a3f..35974251b 100644
--- a/sonoff/support_rotary.ino
+++ b/sonoff/support_rotary.ino
@@ -61,6 +61,10 @@ void update_position(void)
   rotary_state = (s >> 2);
 }
 
+#ifndef ARDUINO_ESP8266_RELEASE_2_3_0      // Fix core 2.5.x ISR not in IRAM Exception
+void update_rotary(void) ICACHE_RAM_ATTR;  // As iram is tight and it works this way too
+#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
+
 void update_rotary(void)
 {
   if (MI_DESK_LAMP == my_module_type){
diff --git a/sonoff/xdrv_04_light.ino b/sonoff/xdrv_04_light.ino
index 90b4f872e..17a0806bb 100644
--- a/sonoff/xdrv_04_light.ino
+++ b/sonoff/xdrv_04_light.ino
@@ -1005,8 +1005,8 @@ unsigned int arilux_rf_repeat_count = 0;
 uint8_t arilux_rf_toggle = 0;
 
 
-#ifndef ARDUINO_ESP8266_RELEASE_2_3_0
-#ifndef USE_WS2812_DMA  // Collides with Neopixelbus but solves RF misses
+#ifndef ARDUINO_ESP8266_RELEASE_2_3_0          // Fix core 2.5.x ISR not in IRAM Exception
+#ifndef USE_WS2812_DMA                         // Collides with Neopixelbus but solves RF misses
 void AriluxRfInterrupt(void) ICACHE_RAM_ATTR;  // As iram is tight and it works this way too
 #endif  // USE_WS2812_DMA
 #endif  // ARDUINO_ESP8266_RELEASE_2_3_0
diff --git a/sonoff/xnrg_01_hlw8012.ino b/sonoff/xnrg_01_hlw8012.ino
index d2da0e3a7..c098870e4 100644
--- a/sonoff/xnrg_01_hlw8012.ino
+++ b/sonoff/xnrg_01_hlw8012.ino
@@ -68,6 +68,7 @@ uint8_t hlw_model_type = 0;
 uint8_t hlw_load_off = 1;
 uint8_t hlw_cf1_timer = 0;
 
+// Fix core 2.5.x ISR not in IRAM Exception
 #ifndef USE_WS2812_DMA  // Collides with Neopixelbus but solves exception
 void HlwCfInterrupt(void) ICACHE_RAM_ATTR;
 void HlwCf1Interrupt(void) ICACHE_RAM_ATTR;
diff --git a/sonoff/xsns_01_counter.ino b/sonoff/xsns_01_counter.ino
index 576f868ff..069016a87 100644
--- a/sonoff/xsns_01_counter.ino
+++ b/sonoff/xsns_01_counter.ino
@@ -40,6 +40,13 @@ void CounterUpdate(uint8_t index)
   }
 }
 
+#ifndef ARDUINO_ESP8266_RELEASE_2_3_0       // Fix core 2.5.x ISR not in IRAM Exception
+void CounterUpdate1(void) ICACHE_RAM_ATTR;  // As iram is tight and it works this way too
+void CounterUpdate2(void) ICACHE_RAM_ATTR;  // As iram is tight and it works this way too
+void CounterUpdate3(void) ICACHE_RAM_ATTR;  // As iram is tight and it works this way too
+void CounterUpdate4(void) ICACHE_RAM_ATTR;  // As iram is tight and it works this way too
+#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
+
 void CounterUpdate1(void)
 {
   CounterUpdate(1);
diff --git a/sonoff/xsns_35_tx20.ino b/sonoff/xsns_35_tx20.ino
index b5e8a2091..05d3cbd8b 100644
--- a/sonoff/xsns_35_tx20.ino
+++ b/sonoff/xsns_35_tx20.ino
@@ -80,6 +80,10 @@ uint8_t tx20_wind_direction = 0;
 
 bool tx20_available = false;
 
+#ifndef ARDUINO_ESP8266_RELEASE_2_3_0      // Fix core 2.5.x ISR not in IRAM Exception
+void Tx20StartRead(void) ICACHE_RAM_ATTR;  // As iram is tight and it works this way too
+#endif  // ARDUINO_ESP8266_RELEASE_2_3_0
+
 void Tx20StartRead(void)
 {
   /* La Crosse TX20 Anemometer datagram every 2 seconds