diff --git a/stdlib/3/signal.pyi b/stdlib/3/signal.pyi
index f956e05bb..9e599f92d 100644
--- a/stdlib/3/signal.pyi
+++ b/stdlib/3/signal.pyi
@@ -1,5 +1,7 @@
 """Stub file for the 'signal' module."""
 
+import sys
+from enum import IntEnum
 from typing import Any, Callable, List, Tuple, Dict, Generic, Union, Optional, Iterable, Set
 from types import FrameType
 
@@ -10,54 +12,115 @@ ITIMER_REAL = ...  # type: int
 ITIMER_VIRTUAL = ...  # type: int
 
 NSIG = ...  # type: int
-SIGABRT = ...  # type: int
-SIGALRM = ...  # type: int
-SIGBUS = ...  # type: int
-SIGCHLD = ...  # type: int
-SIGCLD = ...  # type: int
-SIGCONT = ...  # type: int
-SIGFPE = ...  # type: int
-SIGHUP = ...  # type: int
-SIGILL = ...  # type: int
-SIGINT = ...  # type: int
-SIGIO = ...  # type: int
-SIGIOT = ...  # type: int
-SIGKILL = ...  # type: int
-SIGPIPE = ...  # type: int
-SIGPOLL = ...  # type: int
-SIGPROF = ...  # type: int
-SIGPWR = ...  # type: int
-SIGQUIT = ...  # type: int
-SIGRTMAX = ...  # type: int
-SIGRTMIN = ...  # type: int
-SIGSEGV = ...  # type: int
-SIGSTOP = ...  # type: int
-SIGSYS = ...  # type: int
-SIGTERM = ...  # type: int
-SIGTRAP = ...  # type: int
-SIGTSTP = ...  # type: int
-SIGTTIN = ...  # type: int
-SIGTTOU = ...  # type: int
-SIGURG = ...  # type: int
-SIGUSR1 = ...  # type: int
-SIGUSR2 = ...  # type: int
-SIGVTALRM = ...  # type: int
-SIGWINCH = ...  # type: int
-SIGXCPU = ...  # type: int
-SIGXFSZ = ...  # type: int
 
-SIG_DFL = ...  # type: int
-SIG_IGN = ...  # type: int
+if sys.version_info >= (3, 5):
+    class Signals(IntEnum):
+        SIGABRT = ...
+        SIGALRM = ...
+        SIGBUS = ...
+        SIGCHLD = ...
+        SIGCLD = ...
+        SIGCONT = ...
+        SIGFPE = ...
+        SIGHUP = ...
+        SIGILL = ...
+        SIGINT = ...
+        SIGIO = ...
+        SIGIOT = ...
+        SIGKILL = ...
+        SIGPIPE = ...
+        SIGPOLL = ...
+        SIGPROF = ...
+        SIGPWR = ...
+        SIGQUIT = ...
+        SIGRTMAX = ...
+        SIGRTMIN = ...
+        SIGSEGV = ...
+        SIGSTOP = ...
+        SIGSYS = ...
+        SIGTERM = ...
+        SIGTRAP = ...
+        SIGTSTP = ...
+        SIGTTIN = ...
+        SIGTTOU = ...
+        SIGURG = ...
+        SIGUSR1 = ...
+        SIGUSR2 = ...
+        SIGVTALRM = ...
+        SIGWINCH = ...
+        SIGXCPU = ...
+        SIGXFSZ = ...
+
+    class Handlers(IntEnum):
+        SIG_DFL = ...
+        SIG_IGN = ...
+
+    SIG_DFL = Handlers.SIG_DFL
+    SIG_IGN = Handlers.SIG_IGN
+
+    class Sigmasks(IntEnum):
+        SIG_BLOCK = ...
+        SIG_UNBLOCK = ...
+        SIG_SETMASK = ...
+
+    SIG_BLOCK = Sigmasks.SIG_BLOCK
+    SIG_UNBLOCK = Sigmasks.SIG_UNBLOCK
+    SIG_SETMASK = Sigmasks.SIG_SETMASK
+
+    _SIG = Signals
+    _SIGNUM = Union[int, Signals]
+    _HANDLER = Union[Callable[[Signals, FrameType], None], int, Handlers, None]
+else:
+    SIG_DFL = ...  # type: int
+    SIG_IGN = ...  # type: int
+
+    SIG_BLOCK = ...  # type: int
+    SIG_UNBLOCK = ...  # type: int
+    SIG_SETMASK = ...  # type: int
+
+    _SIG = int
+    _SIGNUM = int
+    _HANDLER = Union[Callable[[int, FrameType], None], int, None]
+
+SIGABRT = ...  # type: _SIG
+SIGALRM = ...  # type: _SIG
+SIGBUS = ...  # type: _SIG
+SIGCHLD = ...  # type: _SIG
+SIGCLD = ...  # type: _SIG
+SIGCONT = ...  # type: _SIG
+SIGFPE = ...  # type: _SIG
+SIGHUP = ...  # type: _SIG
+SIGILL = ...  # type: _SIG
+SIGINT = ...  # type: _SIG
+SIGIO = ...  # type: _SIG
+SIGIOT = ...  # type: _SIG
+SIGKILL = ...  # type: _SIG
+SIGPIPE = ...  # type: _SIG
+SIGPOLL = ...  # type: _SIG
+SIGPROF = ...  # type: _SIG
+SIGPWR = ...  # type: _SIG
+SIGQUIT = ...  # type: _SIG
+SIGRTMAX = ...  # type: _SIG
+SIGRTMIN = ...  # type: _SIG
+SIGSEGV = ...  # type: _SIG
+SIGSTOP = ...  # type: _SIG
+SIGSYS = ...  # type: _SIG
+SIGTERM = ...  # type: _SIG
+SIGTRAP = ...  # type: _SIG
+SIGTSTP = ...  # type: _SIG
+SIGTTIN = ...  # type: _SIG
+SIGTTOU = ...  # type: _SIG
+SIGURG = ...  # type: _SIG
+SIGUSR1 = ...  # type: _SIG
+SIGUSR2 = ...  # type: _SIG
+SIGVTALRM = ...  # type: _SIG
+SIGWINCH = ...  # type: _SIG
+SIGXCPU = ...  # type: _SIG
+SIGXFSZ = ...  # type: _SIG
 
 CTRL_C_EVENT = 0 # Windows
 CTRL_BREAK_EVENT = 0 # Windows
 
-SIG_BLOCK = ...  # type: int
-SIG_UNBLOCK = ...  # type: int
-SIG_SETMASK = ...  # type: int
-
-_HANDLER = Union[Callable[[int, FrameType], None], int, None]
-
 class struct_siginfo(Tuple[int, int, int, int, int, int, int]):
     def __init__(self, sequence: Iterable[int]) -> None: ...
     @property
@@ -82,7 +145,7 @@ def default_int_handler(signum: int, frame: FrameType) -> None:
 
 def getitimer(which: int) -> Tuple[float, float]: ...
 
-def getsignal(signalnum: int) -> _HANDLER:
+def getsignal(signalnum: _SIGNUM) -> _HANDLER:
     raise ValueError()
 
 def pause() -> None: ...
@@ -90,7 +153,7 @@ def pause() -> None: ...
 def pthread_kill(thread_id: int, signum: int) -> None:
     raise OSError()
 
-def pthread_sigmask(how: int, mask: Iterable[int]) -> Set[int]:
+def pthread_sigmask(how: int, mask: Iterable[int]) -> Set[_SIGNUM]:
     raise OSError()
 
 def set_wakeup_fd(fd: int) -> int: ...
@@ -100,7 +163,7 @@ def setitimer(which: int, seconds: float, interval: float = ...) -> Tuple[float,
 def siginterrupt(signalnum: int, flag: bool) -> None:
     raise OSError()
 
-def signal(signalnum: int, handler: _HANDLER) -> _HANDLER:
+def signal(signalnum: _SIGNUM, handler: _HANDLER) -> _HANDLER:
     raise OSError()
 
 def sigpending() -> Any:
@@ -110,7 +173,7 @@ def sigtimedwait(sigset: Iterable[int], timeout: float) -> Optional[struct_sigin
     raise OSError()
     raise ValueError()
 
-def sigwait(sigset: Iterable[int]) -> int:
+def sigwait(sigset: Iterable[int]) -> _SIGNUM:
     raise OSError()
 
 def sigwaitinfo(sigset: Iterable[int]) -> struct_siginfo: