diff --git a/setup.py b/setup.py
index 43b6a6a..3666e8f 100644
--- a/setup.py
+++ b/setup.py
@@ -398,7 +398,7 @@
                                libraries=math_libs) )
 
         # math library functions, e.g. sin()
-        exts.append( Extension('math',  ['mathmodule.c'],
+        exts.append( Extension('math',  ['mathmodule.c', '_math.c'],
                                libraries=math_libs) )
         # time operations and variables
         exts.append( Extension('time', ['timemodule.c'],