em.diff

diff --git a/ext/em.cpp b/ext/em.cpp
index e4ee9be..69a70d2 100644
--- a/ext/em.cpp
+++ b/ext/em.cpp
@@ -928,6 +928,17 @@ bool EventMachine_t::_RunSelectOnce()
 				_ReadLoopBreaker();
 		}
 		else if (s < 0) {
+			switch (errno) {
+				case EAGAIN: {
+					rb_sys_fail("The kernel was (perhaps temporarily) unable to allocate the requested number of file descriptors.");
+				}
+				case EBADF: {
+					rb_sys_fail("One of the descriptor sets specified an invalid descriptor.");
+				}
+				case EINVAL: {
+					rb_sys_fail("Somehow EM passed an invalid nfds or invalid timeout to select(2), please report this!");
+				}
+			}
 			// select can fail on error in a handful of ways.
 			// If this happens, then wait for a little while to avoid busy-looping.
 			// If the error was EINTR, we probably caught SIGCHLD or something,