--- mmapmodule.c.orig	2015-04-02 19:05:30.380554538 -0700
+++ mmapmodule.c	2015-04-02 19:11:00.320488207 -0700
@@ -1335,7 +1335,11 @@
             return NULL;
         }
         /* Win9x appears to need us seeked to zero */
-        lseek(fileno, 0, SEEK_SET);
+	if (lseek(fileno, 0, SEEK_SET) == -1) { /* call to lseek() failed */
+	    PyErr_SetFromErrno(PyExc_OSError);
+	    return NULL;
+	}
+
     }
 
     m_obj = (mmap_object *)type->tp_alloc(type, 0);