diff --git a/Makefile b/Makefile
index e40c5ff..5d9607c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,4 @@
+include mk/python.mk
 DCURL_DIR := deps/dcurl
 DCURL_LIB := $(DCURL_DIR)/build/libdcurl.so
 DEPS += $(DCURL_LIB)
@@ -19,7 +20,7 @@ TESTS += $(wildcard tests/tangleid/*.sh)
 check: server.py $(DCURL_LIB)
 	@ TMP_PID=`mktemp /tmp/server_pid.XXXXXX`; \
 	echo "Running test suite..." ; \
-	( python $^ & echo $$! > $${TMP_PID} ); \
+	( $(PYTHON) $^ & echo $$! > $${TMP_PID} ); \
 	sleep 3 ; \
 	for i in $(TESTS); do \
 	    ( echo "\n\n==[ $$i ]==\n"; $$i || kill -9 `cat $${TMP_PID}` ) \
diff --git a/README.md b/README.md
index 581325e..1501b71 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,7 @@ Most use cases for micropayments involve a single user or device interacting
 repeatedly with a few vendors.
 
 ## Prerequisites
+This package depends on PyOTA, which is known to work with Python 3.5. However, before PyOTA issue [#203](https://github.com/iotaledger/iota.lib.py/issues/203) is resolved, Python 3.6/3.7 will be excluded for running this package. The build system would detect and validate the environment in advance.
 
 Install dependent packages:
 ```shell
diff --git a/mk/python.mk b/mk/python.mk
new file mode 100644
index 0000000..7f7fa83
--- /dev/null
+++ b/mk/python.mk
@@ -0,0 +1,47 @@
+# check Python version
+PY_FAVORED_VER = 3.5
+PYTHON := $(shell which "python")
+ifndef PYTHON
+PYTHON := $(shell which "python3")
+endif
+
+ifndef PYTHON
+PYTHON := $(shell which "python$(PY_FAVORED_VER)")
+endif
+
+ifndef PYTHON
+$(error "Python is not executable, try to check the PATH environment variable or \
+install python$(PY_FAVORED_VER) package.")
+endif # $(shell which "python")
+
+PY_CHECK_VERSION := $(shell $(PYTHON) -V)
+
+ifeq "$(filter $(PY_FAVORED_VER).%, $(PY_CHECK_VERSION))" ""
+PYTHON := $(shell which "python"$(PY_FAVORED_VER))
+ifdef PYTHON
+$(error "Found python$(PY_FAVORED_VER), but it should be set as \
+default interpreter, try to set $(PYTHON) in PATH environment variable.")
+else
+$(error "$(shell python -V):Unsupported python version, only available for Python$(PY_FAVORED_VER).")
+endif # PYTHON
+endif # "$(filter ...
+
+# check "iota" module in Python installation
+PY_CHECK_MOD_IOTA := $(shell python -c "import iota" 2>/dev/null && \
+                       echo 1 || echo 0)
+ifeq ("$(PY_CHECK_MOD_IOTA)","0")
+PIP := $(shell pip -V && echo 1 || echo 0))
+PIP_CHECK_VERSION := $(findstring python 3, $(PIP) && echo $@ || echo 0)
+endif
+
+ifneq ("$(PIP)", "1")
+$(error "PIP package doesn't pre-configured, try to install it.")
+endif
+
+ifeq ("$(PIP_CHECK_VERSION)", "0")
+PIP_FAVORED_VER = 3
+endif
+
+ifeq ("$(PY_CHECK_MOD_IOTA)", "0")
+$(error "PyOTA package doesn't pre-configured, install the latest version: pip$(PIP_FAVORED_VER) install pyota")
+endif
diff --git a/swarm_node.py b/swarm_node.py
index 5c19b04..70368c1 100644
--- a/swarm_node.py
+++ b/swarm_node.py
@@ -145,8 +145,9 @@ def send_transfer(tag, messages, address, values, dict_tips, debug=0):
         time_end_pow = time.time()
         elapsed_pow = elapsed_pow + (time_end_pow - time_start_pow)
 
-        print("Prepare to broadcast ...")
+        print("Prepare to store and broadcast ...")
         try:
+            api.store_transactions([tx_tryte[0:2673]])
             api.broadcast_transactions([tx_tryte[0:2673]])
         except Exception as e:
             print("Error: %s" % (str(e.context)))