diff --git a/.gitignore b/.gitignore
index db872fac..57fca5e5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 sdk/
+cache/
diff --git a/.travis.yml b/.travis.yml
index 7d34f845..e55f87bd 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,6 +5,9 @@ addons:
     packages:
     - python-serial
     - srecord
+cache:
+  directories:
+    - cache
 install:
 - tar -zxvf tools/esp-open-sdk.tar.gz
 - export PATH=$PATH:$PWD/esp-open-sdk/xtensa-lx106-elf/bin
diff --git a/Makefile b/Makefile
index b06333e6..4c2793b1 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,9 @@
 
 # SDK version NodeMCU is locked to
 SDK_VER:=1.5.1
+SDK_FILE_VER:=$(SDK_VER)_16_01_08
+SDK_FILE_ID:=1046
+SDK_FILE_SIZE:=2185752
 # Ensure we search "our" SDK before the tool-chain's SDK (if any)
 TOP_DIR:=$(abspath $(dir $(lastword $(MAKEFILE_LIST))))
 SDK_DIR:=$(TOP_DIR)/sdk/esp_iot_sdk_v$(SDK_VER)
@@ -171,14 +174,20 @@ $(BINODIR)/%.bin: $(IMAGEODIR)/%.out
 all:	sdk_extracted .subdirs $(OBJS) $(OLIBS) $(OIMAGES) $(OBINS) $(SPECIAL_MKTARGETS)
 
 .PHONY: sdk_extracted
+
 sdk_extracted: $(TOP_DIR)/sdk/.extracted-$(SDK_VER)
 
-$(TOP_DIR)/sdk/.extracted-$(SDK_VER):
+$(TOP_DIR)/sdk/.extracted-$(SDK_VER): $(TOP_DIR)/cache/esp_iot_sdk_v$(SDK_FILE_VER).zip
 	mkdir -p "$(dir $@)"
 	(cd "$(dir $@)" && unzip $(TOP_DIR)/cache/esp_iot_sdk_v$(SDK_VER)*.zip esp_iot_sdk_v$(SDK_VER)/lib/* esp_iot_sdk_v$(SDK_VER)/ld/eagle.rom.addr.v6.ld esp_iot_sdk_v$(SDK_VER)/include/* )
 	rm -f $(SDK_DIR)/lib/liblwip.a
 	touch $@
 
+$(TOP_DIR)/cache/esp_iot_sdk_v$(SDK_FILE_VER).zip:
+	mkdir -p "$(dir $@)"
+	wget --tries=10 --timeout=15 --waitretry=30 --read-timeout=20 --retry-connrefused http://bbs.espressif.com/download/file.php?id=$(SDK_FILE_ID) -O $@ || { rm -f "$@"; exit 1; }
+	[ `wc -c < "$@"` -eq $(SDK_FILE_SIZE) ] || { rm -f "$@"; exit 1; }
+
 clean:
 	$(foreach d, $(SUBDIRS), $(MAKE) -C $(d) clean;)
 	$(RM) -r $(ODIR)/$(TARGET)/$(FLAVOR)
diff --git a/app/include/user_version.h b/app/include/user_version.h
index 32aa362a..7fb7d949 100644
--- a/app/include/user_version.h
+++ b/app/include/user_version.h
@@ -3,7 +3,7 @@
 
 #define NODE_VERSION_MAJOR		1U
 #define NODE_VERSION_MINOR		5U
-#define NODE_VERSION_REVISION	0U
+#define NODE_VERSION_REVISION	1U
 #define NODE_VERSION_INTERNAL   0U
 
 #define NODE_VERSION	"NodeMCU 1.5.1"
diff --git a/cache/esp_iot_sdk_v1.5.1_16_01_08.zip b/cache/esp_iot_sdk_v1.5.1_16_01_08.zip
deleted file mode 100644
index 0e6e4e32..00000000
Binary files a/cache/esp_iot_sdk_v1.5.1_16_01_08.zip and /dev/null differ