Index: src/OFHTTPClient.m
==================================================================
--- src/OFHTTPClient.m
+++ src/OFHTTPClient.m
@@ -118,10 +118,11 @@
 	OFURL *URL = request.URL;
 	OFString *path;
 	OFString *user = URL.user, *password = URL.password;
 	OFMutableString *requestString;
 	OFMutableDictionary OF_GENERIC(OFString *, OFString *) *headers;
+	bool hasContentLength, chunked;
 	OFEnumerator OF_GENERIC(OFString *) *keyEnumerator, *objectEnumerator;
 	OFString *key, *object;
 
 	if (URL.path != nil)
 		path = URL.URLEncodedPath;
@@ -185,11 +186,15 @@
 	    request.protocolVersion.minor == 0 &&
 	    [headers objectForKey: @"Connection"] == nil)
 		[headers setObject: @"keep-alive"
 			    forKey: @"Connection"];
 
-	if ([headers objectForKey: @"Content-Length"] != nil &&
+	hasContentLength = ([headers objectForKey: @"Content-Length"] != nil);
+	chunked = [[headers objectForKey: @"Transfer-Encoding"]
+	    isEqual: @"chunked"];
+
+	if ((hasContentLength || chunked) &&
 	    [headers objectForKey: @"Content-Type"] == nil)
 		[headers setObject: @"application/x-www-form-"
 				    @"urlencoded; charset=UTF-8"
 			    forKey: @"Content-Type"];
 
@@ -551,11 +556,11 @@
 	    encoding: (of_string_encoding_t)encoding
 	bytesWritten: (size_t)bytesWritten
 	   exception: (id)exception
 {
 	OFDictionary OF_GENERIC(OFString *, OFString *) *headers;
-	OFString *transferEncoding;
+	bool chunked;
 
 	if (exception != nil) {
 		if ([exception isKindOfClass: [OFWriteFailedException class]] &&
 		    ([exception errNo] == ECONNRESET ||
 		    [exception errNo] == EPIPE)) {
@@ -569,14 +574,14 @@
 	}
 
 	_firstLine = true;
 
 	headers = _request.headers;
-	transferEncoding = [headers objectForKey: @"Transfer-Encoding"];
+	chunked = [[headers objectForKey: @"Transfer-Encoding"]
+	    isEqual: @"chunked"];
 
-	if ([transferEncoding isEqual: @"chunked"] ||
-	    [headers objectForKey: @"Content-Length"] != nil) {
+	if (chunked || [headers objectForKey: @"Content-Length"] != nil) {
 		stream.delegate = nil;
 
 		OFStream *requestBody = [[[OFHTTPClientRequestBodyStream alloc]
 		    initWithHandler: self
 			     socket: (OFTCPSocket *)stream] autorelease];
@@ -723,11 +728,11 @@
 		transferEncoding = [headers objectForKey: @"Transfer-Encoding"];
 		_chunked = [transferEncoding isEqual: @"chunked"];
 
 		contentLengthString = [headers objectForKey: @"Content-Length"];
 		if (contentLengthString != nil) {
-			if (_chunked)
+			if (_chunked || contentLengthString.length == 0)
 				@throw [OFInvalidArgumentException
 				    exception];
 
 			contentLength = contentLengthString.decimalValue;
 			if (contentLength < 0)
@@ -867,11 +872,11 @@
 	_chunked = [[headers objectForKey: @"Transfer-Encoding"]
 	    isEqual: @"chunked"];
 
 	contentLength = [headers objectForKey: @"Content-Length"];
 	if (contentLength != nil) {
-		if (_chunked)
+		if (_chunked || contentLength.length == 0)
 			@throw [OFInvalidServerReplyException exception];
 
 		_hasContentLength = true;
 
 		@try {
@@ -1001,12 +1006,11 @@
 				@throw [OFInvalidServerReplyException
 				    exception];
 		}
 
 		@try {
-			_toRead = line.hexadecimalValue;
-			if (_toRead < 0)
+			if ((_toRead = line.hexadecimalValue) < 0)
 				@throw [OFOutOfRangeException exception];
 		} @catch (OFInvalidFormatException *e) {
 			@throw [OFInvalidServerReplyException exception];
 		}
 

Index: src/OFHTTPServer.m
==================================================================
--- src/OFHTTPServer.m
+++ src/OFHTTPServer.m
@@ -413,11 +413,11 @@
 		OFString *contentLengthString =
 		    [_headers objectForKey: @"Content-Length"];
 		intmax_t contentLength = 0;
 
 		if (contentLengthString != nil) {
-			if (chunked)
+			if (chunked || contentLengthString.length == 0)
 				return [self sendErrorAndClose: 400];
 
 			@try {
 				contentLength =
 				    contentLengthString.decimalValue;
@@ -717,12 +717,11 @@
 				@throw [OFTruncatedDataException exception];
 			else
 				@throw [OFInvalidFormatException exception];
 		}
 
-		_toRead = line.hexadecimalValue;
-		if (_toRead < 0)
+		if ((_toRead = line.hexadecimalValue) < 0)
 			@throw [OFOutOfRangeException exception];
 
 		if (_toRead == 0) {
 			_setAtEndOfStream = true;
 			_toRead = -2;