diff --git a/.python-version b/.python-version
new file mode 100644
index 0000000000..7bcbb3808b
--- /dev/null
+++ b/.python-version
@@ -0,0 +1 @@
+3.4.9
diff --git a/.travis.yml b/.travis.yml
index dec517f0a2..4f57c6f6ec 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -43,7 +43,7 @@ jobs:
       env:
       cache: false
       language: python
-      python: '3.6'
+      python: '3.4' # Oldest supported version according to doc/dependencies.md
       install:
         - set -o errexit; source .travis/lint_04_install.sh
       before_script:
diff --git a/test/functional/test_framework/script.py b/test/functional/test_framework/script.py
index 2c5ba24a6a..012c80a1be 100644
--- a/test/functional/test_framework/script.py
+++ b/test/functional/test_framework/script.py
@@ -450,6 +450,10 @@ def join(self, iterable):
         # join makes no sense for a CScript()
         raise NotImplementedError
 
+    # Python 3.4 compatibility
+    def hex(self):
+        return hexlify(self).decode('ascii')
+
     def __new__(cls, value=b''):
         if isinstance(value, bytes) or isinstance(value, bytearray):
             return super(CScript, cls).__new__(cls, value)
diff --git a/test/lint/check-doc.py b/test/lint/check-doc.py
index b0d9f87958..4facd6c334 100755
--- a/test/lint/check-doc.py
+++ b/test/lint/check-doc.py
@@ -26,8 +26,12 @@
 
 
 def main():
-    used = check_output(CMD_GREP_ARGS, shell=True, universal_newlines=True, encoding='utf8')
-    docd = check_output(CMD_GREP_DOCS, shell=True, universal_newlines=True, encoding='utf8')
+    if sys.version_info >= (3, 6):
+        used = check_output(CMD_GREP_ARGS, shell=True, universal_newlines=True, encoding='utf8')
+        docd = check_output(CMD_GREP_DOCS, shell=True, universal_newlines=True, encoding='utf8')
+    else:
+        used = check_output(CMD_GREP_ARGS, shell=True, universal_newlines=True) # encoding='utf8'
+        docd = check_output(CMD_GREP_DOCS, shell=True, universal_newlines=True) # encoding='utf8'
 
     args_used = set(re.findall(re.compile(REGEX_ARG), used))
     args_docd = set(re.findall(re.compile(REGEX_DOC), docd)).union(SET_DOC_OPTIONAL)