diff --git a/doc/conf.py b/doc/conf.py
index 5d92815da56..9700787e1a6 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -53,6 +53,10 @@ project = u'Zephyr Project'
 copyright = u'2015-2017 Zephyr Project members and individual contributors.'
 author = u'many'
 
+if "ZEPHYR_BASE" not in os.environ:
+    sys.stderr.write("$ZEPHYR_BASE environment variable undefined.\n")
+    exit(1)
+ZEPHYR_BASE = os.environ["ZEPHYR_BASE"]
 
 # The following code tries to extract the information by reading the Makefile,
 # when Sphinx is run directly (e.g. by Read the Docs).
@@ -61,7 +65,7 @@ try:
     version_minor = None
     patchlevel = None
     extraversion = None
-    for line in open('../VERSION'):
+    for line in open(os.path.join(ZEPHYR_BASE, 'VERSION')):
         key, val = [x.strip() for x in line.split('=', 2)]
         if key == 'VERSION_MAJOR':
             version_major = val
@@ -76,7 +80,7 @@ try:
 except:
     pass
 finally:
-    if version_major and version_minor and patchlevel and extraversion:
+    if version_major and version_minor and patchlevel and extraversion is not None :
         version = release = version_major + '.' + version_minor + '.' + patchlevel
         if extraversion != '':
             version = release = version + '-' + extraversion