diff --git a/gunicorn/http/errors.py b/gunicorn/http/errors.py
index 6f9ab3a6..879d430b 100644
--- a/gunicorn/http/errors.py
+++ b/gunicorn/http/errors.py
@@ -35,18 +35,19 @@ class InvalidHTTPVersion(ParseException):
         return "Invalid HTTP Version: %s" % self.version
 
 class InvalidHeader(ParseException):
-    def __init__(self, hdr):
+    def __init__(self, hdr, req=None):
         self.hdr = hdr
+        self.req = req
 
     def __str__(self):
-        return "Invalid HTTP Header: %r" % self.hdr
+        return "Invalid HTTP Header: %s" % self.hdr
 
 class InvalidHeaderName(ParseException):
     def __init__(self, hdr):
         self.hdr = hdr
 
     def __str__(self):
-        return "Invalid HTTP header name: %r" % self.hdr
+        return "Invalid HTTP header name: %s" % self.hdr
 
 class InvalidChunkSize(ParseException):
     def __init__(self, data):
diff --git a/gunicorn/http/message.py b/gunicorn/http/message.py
index 8bc4b4cd..4bd554c7 100644
--- a/gunicorn/http/message.py
+++ b/gunicorn/http/message.py
@@ -94,25 +94,27 @@ class Message(object):
 
     def set_body_reader(self):
         chunked = False
-        response_length = None
+        content_length = None
         for (name, value) in self.headers:
             if name == "CONTENT-LENGTH":
-                try:
-                    response_length = int(value)
-                except ValueError:
-                    response_length = None
+                content_length = value
             elif name == "TRANSFER-ENCODING":
                 chunked = value.lower() == "chunked"
             elif name == "SEC-WEBSOCKET-KEY1":
-                response_length = 8
-
-            if response_length is not None or chunked:
-                break
+                content_length = 8
 
         if chunked:
             self.body = Body(ChunkedReader(self, self.unreader))
-        elif response_length is not None:
-            self.body = Body(LengthReader(self.unreader, response_length))
+        elif content_length is not None:
+            try:
+                content_length = int(content_length)
+            except ValueError:
+                raise InvalidHeader("CONTENT-LENGTH", req=self)
+
+            if content_length < 0:
+                raise InvalidHeader("CONTENT-LENGTH", req=self)
+
+            self.body = Body(LengthReader(self.unreader, content_length))
         else:
             self.body = Body(EOFReader(self.unreader))
 
diff --git a/gunicorn/workers/base.py b/gunicorn/workers/base.py
index 7e8cee07..2392e8dd 100644
--- a/gunicorn/workers/base.py
+++ b/gunicorn/workers/base.py
@@ -142,7 +142,9 @@ class Worker(object):
             elif isinstance(exc, InvalidHTTPVersion):
                 mesg = "<p>Invalid HTTP Version '%s'</p>" % str(exc)
             elif isinstance(exc, (InvalidHeaderName, InvalidHeader,)):
-                mesg = "<p>Invalid Header '%s'</p>" % str(exc)
+                mesg = "<p>%s</p>" % str(exc)
+                if not req and hasattr(exc, "req"):
+                    req = exc.req # for access log
             elif isinstance(exc, LimitRequestLine):
                 mesg = "<p>%s</p>" % str(exc)
             elif isinstance(exc, LimitRequestHeaders):
diff --git a/tests/requests/invalid/014.http b/tests/requests/invalid/014.http
new file mode 100644
index 00000000..a5356704
--- /dev/null
+++ b/tests/requests/invalid/014.http
@@ -0,0 +1,4 @@
+PUT /stuff/here?foo=bar HTTP/1.0\r\n
+CONTENT-LENGTH: -1\r\n
+\r\n
+{"test": "-1}
\ No newline at end of file
diff --git a/tests/requests/invalid/014.py b/tests/requests/invalid/014.py
new file mode 100644
index 00000000..4dcf8254
--- /dev/null
+++ b/tests/requests/invalid/014.py
@@ -0,0 +1,3 @@
+from gunicorn.http.errors import InvalidHeader
+
+request = InvalidHeader
diff --git a/tests/requests/invalid/015.http b/tests/requests/invalid/015.http
new file mode 100644
index 00000000..7d774cf6
--- /dev/null
+++ b/tests/requests/invalid/015.http
@@ -0,0 +1,4 @@
+POST /stuff/here?foo=bar HTTP/1.0\r\n
+CONTENT-LENGTH: bla-bla-bla\r\n
+\r\n
+{"test": "-1}
\ No newline at end of file
diff --git a/tests/requests/invalid/015.py b/tests/requests/invalid/015.py
new file mode 100644
index 00000000..4dcf8254
--- /dev/null
+++ b/tests/requests/invalid/015.py
@@ -0,0 +1,3 @@
+from gunicorn.http.errors import InvalidHeader
+
+request = InvalidHeader
diff --git a/tests/requests/valid/025.http b/tests/requests/valid/025.http
new file mode 100644
index 00000000..62267add
--- /dev/null
+++ b/tests/requests/valid/025.http
@@ -0,0 +1,19 @@
+POST /chunked_cont_h_at_first HTTP/1.1\r\n
+Content-Length: -1\r\n
+Transfer-Encoding: chunked\r\n
+\r\n
+5; some; parameters=stuff\r\n
+hello\r\n
+6; blahblah; blah\r\n
+ world\r\n
+0\r\n
+\r\n
+PUT /chunked_cont_h_at_last HTTP/1.1\r\n
+Transfer-Encoding: chunked\r\n
+Content-Length: -1\r\n
+\r\n
+5; some; parameters=stuff\r\n
+hello\r\n
+6; blahblah; blah\r\n
+ world\r\n
+0\r\n
\ No newline at end of file
diff --git a/tests/requests/valid/025.py b/tests/requests/valid/025.py
new file mode 100644
index 00000000..7e8f1826
--- /dev/null
+++ b/tests/requests/valid/025.py
@@ -0,0 +1,23 @@
+req1 = {
+    "method": "POST",
+    "uri": uri("/chunked_cont_h_at_first"),
+    "version": (1, 1),
+    "headers": [
+        ("CONTENT-LENGTH", "-1"),
+        ("TRANSFER-ENCODING", "chunked")
+    ],
+    "body": "hello world"
+}
+
+req2 = {
+    "method": "PUT",
+    "uri": uri("/chunked_cont_h_at_last"),
+    "version": (1, 1),
+    "headers": [
+        ("TRANSFER-ENCODING", "chunked"),
+        ("CONTENT-LENGTH", "-1"),
+    ],
+    "body": "hello world"
+}
+
+request = [req1, req2]