Index: src/OFKernelEventObserver_select.m
==================================================================
--- src/OFKernelEventObserver_select.m
+++ src/OFKernelEventObserver_select.m
@@ -61,11 +61,11 @@
 
 - (void)OF_addObjectForReading: (id)object
 {
 	int fd = [object fileDescriptorForReading];
 
-	if (fd > INT_MAX - 1)
+	if (fd < 0 || fd > INT_MAX - 1)
 		@throw [OFOutOfRangeException exception];
 
 #ifndef _WIN32
 	if (fd >= FD_SETSIZE)
 		@throw [OFOutOfRangeException exception];
@@ -79,11 +79,11 @@
 
 - (void)OF_addObjectForWriting: (id)object
 {
 	int fd = [object fileDescriptorForWriting];
 
-	if (fd > INT_MAX - 1)
+	if (fd < 0 || fd > INT_MAX - 1)
 		@throw [OFOutOfRangeException exception];
 
 #ifndef _WIN32
 	if (fd >= FD_SETSIZE)
 		@throw [OFOutOfRangeException exception];
@@ -99,11 +99,11 @@
 {
 	/* TODO: Adjust _maxFD */
 
 	int fd = [object fileDescriptorForReading];
 
-	if (fd >= FD_SETSIZE)
+	if (fd < 0 || fd >= FD_SETSIZE)
 		@throw [OFOutOfRangeException exception];
 
 	FD_CLR(fd, &_readFDs);
 }
 
@@ -111,11 +111,11 @@
 {
 	/* TODO: Adjust _maxFD */
 
 	int fd = [object fileDescriptorForWriting];
 
-	if (fd >= FD_SETSIZE)
+	if (fd < 0 || fd >= FD_SETSIZE)
 		@throw [OFOutOfRangeException exception];
 
 	FD_CLR(fd, &_writeFDs);
 }
 
@@ -175,13 +175,14 @@
 
 	objects = [_readObjects objects];
 	count = [_readObjects count];
 
 	for (i = 0; i < count; i++) {
-		int fd = [objects[i] fileDescriptorForReading];
+		int fd;
 
 		pool = objc_autoreleasePoolPush();
+		fd = [objects[i] fileDescriptorForReading];
 
 		if (FD_ISSET(fd, &readFDs) && [_delegate respondsToSelector:
 		    @selector(objectIsReadyForReading:)])
 			[_delegate objectIsReadyForReading: objects[i]];
 
@@ -190,17 +191,18 @@
 
 	objects = [_writeObjects objects];
 	count = [_writeObjects count];
 
 	for (i = 0; i < count; i++) {
-		int fd = [objects[i] fileDescriptorForWriting];
+		int fd;
 
 		pool = objc_autoreleasePoolPush();
+		fd = [objects[i] fileDescriptorForWriting];
 
 		if (FD_ISSET(fd, &writeFDs) && [_delegate respondsToSelector:
 		    @selector(objectIsReadyForWriting:)])
 			[_delegate objectIsReadyForWriting: objects[i]];
 
 		objc_autoreleasePoolPop(pool);
 	}
 }
 @end