diff --git a/setup/__init__.py b/setup/__init__.py
index b54c09efed..12097a387c 100644
--- a/setup/__init__.py
+++ b/setup/__init__.py
@@ -46,13 +46,13 @@ def require_clean_git():
 def initialize_constants():
     global __version__, __appname__, modules, functions, basenames, scripts
 
-    src = open('src/calibre/constants.py', 'rb').read()
+    src = open(os.path.join(SRC, 'calibre/constants.py'), 'rb').read()
     nv = re.search(r'numeric_version\s+=\s+\((\d+), (\d+), (\d+)\)', src)
     __version__ = '%s.%s.%s'%(nv.group(1), nv.group(2), nv.group(3))
     __appname__ = re.search(r'__appname__\s+=\s+(u{0,1})[\'"]([^\'"]+)[\'"]',
             src).group(2)
     epsrc = re.compile(r'entry_points = (\{.*?\})', re.DOTALL).\
-            search(open('src/calibre/linux.py', 'rb').read()).group(1)
+            search(open(os.path.join(SRC, 'calibre/linux.py'), 'rb').read()).group(1)
     entry_points = eval(epsrc, {'__appname__': __appname__})
 
     def e2b(ep):