diff --git a/uvloop/includes/stdlib.pxi b/uvloop/includes/stdlib.pxi
index 3c27687..a5ef795 100644
--- a/uvloop/includes/stdlib.pxi
+++ b/uvloop/includes/stdlib.pxi
@@ -116,6 +116,7 @@ cdef os_fspath = os.fspath
 cdef stat_S_ISSOCK = stat.S_ISSOCK
 
 cdef sys_ignore_environment = sys.flags.ignore_environment
+cdef sys_dev_mode = sys.flags.dev_mode
 cdef sys_exc_info = sys.exc_info
 cdef sys_set_coroutine_wrapper = getattr(sys, 'set_coroutine_wrapper', None)
 cdef sys_get_coroutine_wrapper = getattr(sys, 'get_coroutine_wrapper', None)
diff --git a/uvloop/loop.pyx b/uvloop/loop.pyx
index 86141cb..05f9f0e 100644
--- a/uvloop/loop.pyx
+++ b/uvloop/loop.pyx
@@ -223,8 +223,9 @@ cdef class Loop:
         return main_thread_id == PyThread_get_thread_ident()
 
     def __init__(self):
-        self.set_debug((not sys_ignore_environment
-                        and bool(os_environ.get('PYTHONASYNCIODEBUG'))))
+        self.set_debug(
+            sys_dev_mode or (not sys_ignore_environment
+                             and bool(os_environ.get('PYTHONASYNCIODEBUG'))))
 
     def __dealloc__(self):
         if self._running == 1: