Index: src/OFDatagramSocket.m
==================================================================
--- src/OFDatagramSocket.m
+++ src/OFDatagramSocket.m
@@ -116,11 +116,11 @@
 		@throw [OFSetOptionFailedException exceptionWithObject: self
 								 errNo: errno];
 
 	_canBlock = canBlock;
 #elif defined(OF_WINDOWS)
-	u_long v = canBlock;
+	u_long v = !canBlock;
 
 	if (ioctlsocket(_socket, FIONBIO, &v) == SOCKET_ERROR)
 		@throw [OFSetOptionFailedException
 		    exceptionWithObject: self
 				  errNo: OFSocketErrNo()];

Index: src/OFSequencedPacketSocket.m
==================================================================
--- src/OFSequencedPacketSocket.m
+++ src/OFSequencedPacketSocket.m
@@ -133,11 +133,11 @@
 		@throw [OFSetOptionFailedException exceptionWithObject: self
 								 errNo: errno];
 
 	_canBlock = canBlock;
 #elif defined(OF_WINDOWS)
-	u_long v = canBlock;
+	u_long v = !canBlock;
 
 	if (ioctlsocket(_socket, FIONBIO, &v) == SOCKET_ERROR)
 		@throw [OFSetOptionFailedException
 		    exceptionWithObject: self
 				  errNo: OFSocketErrNo()];

Index: src/OFStreamSocket.m
==================================================================
--- src/OFStreamSocket.m
+++ src/OFStreamSocket.m
@@ -162,13 +162,13 @@
 
 #if defined(OF_WINDOWS) || defined(OF_AMIGAOS)
 - (void)setCanBlock: (bool)canBlock
 {
 # ifdef OF_WINDOWS
-	u_long v = canBlock;
+	u_long v = !canBlock;
 # else
-	char v = canBlock;
+	char v = !canBlock;
 # endif
 
 	if (ioctlsocket(_socket, FIONBIO, &v) == SOCKET_ERROR)
 		@throw [OFSetOptionFailedException
 		    exceptionWithObject: self