@@ -40,10 +40,11 @@
 #import "OFTimer.h"
 #import "OFTimer+Private.h"
 #import "OFDate.h"
 
 #import "OFObserveFailedException.h"
+#import "OFWriteFailedException.h"
 
 #include "OFRunLoopConstants.inc"
 
 static OFRunLoop *mainRunLoop = nil;
 
@@ -567,19 +568,24 @@
 	size_t dataLength = _data.count * _data.itemSize;
 	OFData *newData, *oldData;
 
 	@try {
 		const char *dataItems = _data.items;
+		length = dataLength - _writtenLength;
+		[object writeBuffer: dataItems + _writtenLength length: length];
+	} @catch (OFWriteFailedException *e) {
+		length = e.bytesWritten;
 
-		length = [object writeBuffer: dataItems + _writtenLength
-				      length: dataLength - _writtenLength];
+		if (e.errNo != EWOULDBLOCK)
+			exception = e;
 	} @catch (id e) {
 		length = 0;
 		exception = e;
 	}
 
 	_writtenLength += length;
+	OFEnsure(_writtenLength <= dataLength);
 
 	if (_writtenLength != dataLength && exception == nil)
 		return true;
 
 # ifdef OF_HAVE_BLOCKS
@@ -639,19 +645,24 @@
 	size_t cStringLength = [_string cStringLengthWithEncoding: _encoding];
 	OFString *newString, *oldString;
 
 	@try {
 		const char *cString = [_string cStringWithEncoding: _encoding];
+		length = cStringLength - _writtenLength;
+		[object writeBuffer: cString + _writtenLength length: length];
+	} @catch (OFWriteFailedException *e) {
+		length = e.bytesWritten;
 
-		length = [object writeBuffer: cString + _writtenLength
-				      length: cStringLength - _writtenLength];
+		if (e.errNo != EWOULDBLOCK)
+			exception = e;
 	} @catch (id e) {
 		length = 0;
 		exception = e;
 	}
 
 	_writtenLength += length;
+	OFEnsure(_writtenLength <= cStringLength);
 
 	if (_writtenLength != cStringLength && exception == nil)
 		return true;
 
 # ifdef OF_HAVE_BLOCKS