diff --git a/core/MyOTAFirmwareUpdate.cpp b/core/MyOTAFirmwareUpdate.cpp
index ae7577d..1b2aca8 100644
--- a/core/MyOTAFirmwareUpdate.cpp
+++ b/core/MyOTAFirmwareUpdate.cpp
@@ -29,19 +29,20 @@ I2CEeprom _flash(MY_OTA_I2C_ADDR);
 #else
 SPIFlash _flash(MY_OTA_FLASH_SS, MY_OTA_FLASH_JDECID);
 #endif
-nodeFirmwareConfig_t _nodeFirmwareConfig;
-bool _firmwareUpdateOngoing;
-uint32_t _firmwareLastRequest;
-uint16_t _firmwareBlock;
-uint8_t _firmwareRetry;
 
-void readFirmwareSettings(void)
+LOCAL nodeFirmwareConfig_t _nodeFirmwareConfig;
+LOCAL bool _firmwareUpdateOngoing = false;
+LOCAL uint32_t _firmwareLastRequest;
+LOCAL uint16_t _firmwareBlock;
+LOCAL uint8_t _firmwareRetry;
+
+LOCAL void readFirmwareSettings(void)
 {
 	hwReadConfigBlock((void*)&_nodeFirmwareConfig, (void*)EEPROM_FIRMWARE_TYPE_ADDRESS,
 	                  sizeof(nodeFirmwareConfig_t));
 }
 
-void firmwareOTAUpdateRequest(void)
+LOCAL void firmwareOTAUpdateRequest(void)
 {
 	const uint32_t enterMS = hwMillis();
 	if (_firmwareUpdateOngoing && (enterMS - _firmwareLastRequest > MY_OTA_RETRY_DELAY)) {
@@ -67,9 +68,13 @@ void firmwareOTAUpdateRequest(void)
 	}
 }
 
-bool firmwareOTAUpdateProcess(void)
+LOCAL bool firmwareOTAUpdateProcess(void)
 {
 	if (_msg.type == ST_FIRMWARE_CONFIG_RESPONSE) {
+		if(_firmwareUpdateOngoing) {
+			OTA_DEBUG(PSTR("!OTA:FWP:UPDO\n"));	// FW config response received, FW update already ongoing
+			return true;
+		}
 		nodeFirmwareConfig_t *firmwareConfigResponse = (nodeFirmwareConfig_t *)_msg.data;
 		// compare with current node configuration, if they differ, start FW fetch process
 		if (memcmp(&_nodeFirmwareConfig, firmwareConfigResponse, sizeof(nodeFirmwareConfig_t))) {
@@ -163,7 +168,7 @@ bool firmwareOTAUpdateProcess(void)
 	return false;
 }
 
-void presentBootloaderInformation(void)
+LOCAL void presentBootloaderInformation(void)
 {
 	requestFirmwareConfig_t *requestFirmwareConfig = (requestFirmwareConfig_t *)_msgTmp.data;
 	mSetLength(_msgTmp, sizeof(requestFirmwareConfig_t));
@@ -177,12 +182,13 @@ void presentBootloaderInformation(void)
 	(void)_sendRoute(build(_msgTmp, GATEWAY_ADDRESS, NODE_SENSOR_ID, C_STREAM,
 	                       ST_FIRMWARE_CONFIG_REQUEST, false));
 }
-bool isFirmwareUpdateOngoing(void)
+
+LOCAL bool isFirmwareUpdateOngoing(void)
 {
 	return _firmwareUpdateOngoing;
 }
 // do a crc16 on the whole received firmware
-bool transportIsValidFirmware(void)
+LOCAL bool transportIsValidFirmware(void)
 {
 	// init crc
 	uint16_t crc = ~0;
diff --git a/core/MyOTAFirmwareUpdate.h b/core/MyOTAFirmwareUpdate.h
index 0e6c111..3e011df 100644
--- a/core/MyOTAFirmwareUpdate.h
+++ b/core/MyOTAFirmwareUpdate.h
@@ -34,19 +34,20 @@
 *
 * MyOTAFirmwareUpdate debug log messages:
 *
-* |E| SYS | SUB | Message											| Comment
+* |E| SYS | SUB | Message                     | Comment
 * |-|-----|-----|-----------------------------|----------------------------------------------------------------------------
-* | | OTA | FWP | UPDATE											| FW update initiated
-* |!| OTA | FWP | FLASH INIT FAIL							| Failed to initialise flash
-* | | OTA | FWP | UPDATE SKIPPED							| FW update skipped, no newer version available
-* | | OTA | FWP | RECV B=%04X									| Received FW block (B)
-* |!| OTA | FWP | WRONG FWB										| Wrong FW block received
-* | | OTA | FWP | FW END											| FW received, proceed to CRC verification
-* | | OTA | FWP | CRC OK											| FW CRC verification OK
-* |!| OTA | FWP | CRC FAIL										| FW CRC verification failed
-* | | OTA | FRQ | FW REQ,T=%04X,V=%04X,B=%04X	| Request FW update, FW type (T), version (V), block (B)
-* |!| OTA | FRQ | FW UPD FAIL									| FW update failed
-* | | OTA | CRC | B=%04X,C=%04X,F=%04X				| FW CRC verification. FW blocks (B), calculated CRC (C), FW CRC (F)
+* | | OTA | FWP | UPDATE                      | FW update initiated
+* |!| OTA | FWP | UPDO                        | FW config response received, FW update already ongoing
+* |!| OTA | FWP | FLASH INIT FAIL             | Failed to initialise flash
+* | | OTA | FWP | UPDATE SKIPPED              | FW update skipped, no newer version available
+* | | OTA | FWP | RECV B=%04X                 | Received FW block (B)
+* |!| OTA | FWP | WRONG FWB                   | Wrong FW block received
+* | | OTA | FWP | FW END                      | FW received, proceed to CRC verification
+* | | OTA | FWP | CRC OK                      | FW CRC verification OK
+* |!| OTA | FWP | CRC FAIL                    | FW CRC verification failed
+* | | OTA | FRQ | FW REQ,T=%04X,V=%04X,B=%04X | Request FW update, FW type (T), version (V), block (B)
+* |!| OTA | FRQ | FW UPD FAIL                 | FW update failed
+* | | OTA | CRC | B=%04X,C=%04X,F=%04X        | FW CRC verification. FW blocks (B), calculated CRC (C), FW CRC (F)
 *
 *
 * @brief API declaration for MyOTAFirmwareUpdate
@@ -58,6 +59,8 @@
 
 #include "MySensorsCore.h"
 
+#define LOCAL static //!< static
+
 #define FIRMWARE_BLOCK_SIZE		(16u)				//!< Size of each firmware block
 #define FIRMWARE_MAX_REQUESTS	(5u)				//!< Number of times a firmware block should be requested before giving up
 #define MY_OTA_RETRY			(5u)				//!< Number of times to request a fw block before giving up
@@ -120,27 +123,27 @@ typedef struct {
  *
  * Current firmware settings (type, version, crc, blocks) are read into _fc
  */
-void readFirmwareSettings(void);
+LOCAL void readFirmwareSettings(void);
 /**
  * @brief Handle OTA FW update requests
  */
-void firmwareOTAUpdateRequest(void);
+LOCAL void firmwareOTAUpdateRequest(void);
 /**
  * @brief Handle OTA FW update responses
  *
  * This function handles incoming OTA FW packets and stores them to external flash (Sensebender)
  */
-bool firmwareOTAUpdateProcess(void);
+LOCAL bool firmwareOTAUpdateProcess(void);
 /**
  * @brief Validate uploaded FW CRC
  *
  * This function verifies if uploaded FW CRC is valid
  */
-bool transportIsValidFirmware(void);
+LOCAL bool transportIsValidFirmware(void);
 /**
  * @brief Present bootloader/FW information upon startup
  */
-void presentBootloaderInformation(void);
+LOCAL void presentBootloaderInformation(void);
 
 #endif
 
diff --git a/core/MySensorsCore.cpp b/core/MySensorsCore.cpp
index 678b66e..76c36c1 100644
--- a/core/MySensorsCore.cpp
+++ b/core/MySensorsCore.cpp
@@ -542,14 +542,6 @@ int8_t _sleep(const uint32_t sleepingMS, const bool smartSleep, const uint8_t in
 	CORE_DEBUG(PSTR("MCO:SLP:MS=%" PRIu32 ",SMS=%" PRIu8 ",I1=%" PRIu8 ",M1=%" PRIu8 ",I2=%" PRIu8
 	                ",M2=%" PRIu8 "\n"), sleepingMS, smartSleep,
 	           interrupt1, mode1, interrupt2, mode2);
-	// OTA FW feature: do not sleep if FW update ongoing
-#if defined(MY_OTA_FIRMWARE_FEATURE)
-	if (isFirmwareUpdateOngoing()) {
-		CORE_DEBUG(PSTR("!MCO:SLP:FWUPD\n"));	// sleeping not possible, FW update ongoing
-		wait(sleepingMS);
-		return MY_SLEEP_NOT_POSSIBLE;
-	}
-#endif
 	// repeater feature: sleeping not possible
 #if defined(MY_REPEATER_FEATURE)
 	(void)smartSleep;
@@ -583,15 +575,36 @@ int8_t _sleep(const uint32_t sleepingMS, const bool smartSleep, const uint8_t in
 			return MY_SLEEP_NOT_POSSIBLE;
 		}
 	}
+	// OTA FW feature: do not sleep if FW update ongoing
+#if defined(MY_OTA_FIRMWARE_FEATURE)
+	while (isFirmwareUpdateOngoing() && sleepingTimeMS) {
+		CORE_DEBUG(PSTR("!MCO:SLP:FWUPD\n"));	// sleeping not possible, FW update ongoing
+		wait(1000ul);
+		sleepingTimeMS = sleepingTimeMS >= 1000ul ? sleepingTimeMS - 1000ul : 1000ul;
+	}
+#endif // MY_OTA_FIRMWARE_FEATURE
 	if (smartSleep) {
+		// sleeping time left?
+		if (sleepingTimeMS < ((uint32_t)MY_SMART_SLEEP_WAIT_DURATION_MS)) {
+			wait(sleepingMS);
+			CORE_DEBUG(PSTR("!MCO:SLP:NTL\n"));	// sleeping not possible, no time left
+			return MY_SLEEP_NOT_POSSIBLE;
+		}
 		// notify controller about going to sleep, payload indicates smartsleep waiting time in MS
 		(void)_sendRoute(build(_msgTmp, GATEWAY_ADDRESS, NODE_SENSOR_ID, C_INTERNAL,
 		                       I_PRE_SLEEP_NOTIFICATION).set((uint32_t)MY_SMART_SLEEP_WAIT_DURATION_MS));
 		wait(MY_SMART_SLEEP_WAIT_DURATION_MS);		// listen for incoming messages
+#if defined(MY_OTA_FIRMWARE_FEATURE)
+		// check if during smart sleep waiting period a FOTA request was received
+		if (isFirmwareUpdateOngoing()) {
+			CORE_DEBUG(PSTR("!MCO:SLP:FWUPD\n"));	// sleeping not possible, FW update ongoing
+			return MY_SLEEP_NOT_POSSIBLE;
+		}
+#endif // MY_OTA_FIRMWARE_FEATURE
 	}
 #else
 	(void)smartSleep;
-#endif
+#endif // MY_SENSOR_NETWORK
 
 #if defined(MY_SENSOR_NETWORK)
 	transportDisable();
diff --git a/core/MySensorsCore.h b/core/MySensorsCore.h
index 3008e28..70e1913 100644
--- a/core/MySensorsCore.h
+++ b/core/MySensorsCore.h
@@ -52,6 +52,7 @@
 * | | MCO | PIM | NODE REG=%%d																| Registration response received, registration status (REG)
 * | | MCO | SLP | MS=%%lu,SMS=%%d,I1=%%d,M1=%%d,I2=%%d,M2=%%d	| Sleep node, time (MS), smartSleep (SMS), Int1/M1, Int2/M2
 * | | MCO | SLP | WUP=%%d																			| Node woke-up, reason/IRQ (WUP)
+* |!| MCO | SLP | NTL																					| Sleeping not possible, no time left
 * |!| MCO | SLP | FWUPD																				| Sleeping not possible, FW update ongoing
 * |!| MCO | SLP | REP																					| Sleeping not possible, repeater feature enabled
 * |!| MCO | SLP | TNR																					| Transport not ready, attempt to reconnect until timeout (MY_SLEEP_TRANSPORT_RECONNECT_TIMEOUT_MS)