diff --git a/Makefile b/Makefile
index 33c8ba0..b3e0ff4 100644
--- a/Makefile
+++ b/Makefile
@@ -22,14 +22,14 @@ PLATFORM ?= $(shell sh -c 'uname -s | tr "[A-Z]" "[a-z]"')
 HELPER ?=
 BINEXT ?=
 ifeq (darwin,$(PLATFORM))
-SONAME ?= libhttp_parser.2.6.0.dylib
+SONAME ?= libhttp_parser.2.6.1.dylib
 SOEXT ?= dylib
 else ifeq (wine,$(PLATFORM))
 CC = winegcc
 BINEXT = .exe.so
 HELPER = wine
 else
-SONAME ?= libhttp_parser.so.2.6.0
+SONAME ?= libhttp_parser.so.2.6.1
 SOEXT ?= so
 endif
 
diff --git a/http_parser.c b/http_parser.c
index b3037d7..98e0b9f 100644
--- a/http_parser.c
+++ b/http_parser.c
@@ -435,6 +435,12 @@ enum http_host_state
   (IS_ALPHANUM(c) || (c) == '.' || (c) == '-' || (c) == '_')
 #endif
 
+/**
+ * Verify that a char is a valid visible (printable) US-ASCII
+ * character or %x80-FF
+ **/
+#define IS_HEADER_CHAR(ch)                                                     \
+  (ch == CR || ch == LF || ch == 9 || (ch > 31 && ch != 127))
 
 #define start_state (parser->type == HTTP_REQUEST ? s_start_req : s_start_res)
 
@@ -639,6 +645,7 @@ size_t http_parser_execute (http_parser *parser,
   const char *body_mark = 0;
   const char *status_mark = 0;
   enum state p_state = (enum state) parser->state;
+  const unsigned int lenient = parser->lenient_http_headers;
 
   /* We're in an error state. Don't bother doing anything. */
   if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {
@@ -1408,7 +1415,12 @@ reexecute:
                   || c != CONTENT_LENGTH[parser->index]) {
                 parser->header_state = h_general;
               } else if (parser->index == sizeof(CONTENT_LENGTH)-2) {
+                if (parser->flags & F_CONTENTLENGTH) {
+                  SET_ERRNO(HPE_UNEXPECTED_CONTENT_LENGTH);
+                  goto error;
+                }
                 parser->header_state = h_content_length;
+                parser->flags |= F_CONTENTLENGTH;
               }
               break;
 
@@ -1560,6 +1572,11 @@ reexecute:
             REEXECUTE();
           }
 
+          if (!lenient && !IS_HEADER_CHAR(ch)) {
+            SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
+            goto error;
+          }
+
           c = LOWER(ch);
 
           switch (h_state) {
@@ -1727,7 +1744,10 @@ reexecute:
 
       case s_header_almost_done:
       {
-        STRICT_CHECK(ch != LF);
+        if (UNLIKELY(ch != LF)) {
+          SET_ERRNO(HPE_LF_EXPECTED);
+          goto error;
+        }
 
         UPDATE_STATE(s_header_value_lws);
         break;
@@ -1811,6 +1831,14 @@ reexecute:
           REEXECUTE();
         }
 
+        /* Cannot use chunked encoding and a content-length header together
+           per the HTTP specification. */
+        if ((parser->flags & F_CHUNKED) &&
+            (parser->flags & F_CONTENTLENGTH)) {
+          SET_ERRNO(HPE_UNEXPECTED_CONTENT_LENGTH);
+          goto error;
+        }
+
         UPDATE_STATE(s_headers_done);
 
         /* Set this here so that on_headers_complete() callbacks can see it */
diff --git a/http_parser.h b/http_parser.h
index 34bebf3..e33c062 100644
--- a/http_parser.h
+++ b/http_parser.h
@@ -27,7 +27,7 @@ extern "C" {
 /* Also update SONAME in the Makefile whenever you change these. */
 #define HTTP_PARSER_VERSION_MAJOR 2
 #define HTTP_PARSER_VERSION_MINOR 6
-#define HTTP_PARSER_VERSION_PATCH 0
+#define HTTP_PARSER_VERSION_PATCH 1
 
 #include <sys/types.h>
 #if defined(_WIN32) && !defined(__MINGW32__) && \
@@ -148,6 +148,7 @@ enum flags
   , F_TRAILING              = 1 << 4
   , F_UPGRADE               = 1 << 5
   , F_SKIPBODY              = 1 << 6
+  , F_CONTENTLENGTH         = 1 << 7
   };
 
 
@@ -190,6 +191,8 @@ enum flags
   XX(INVALID_HEADER_TOKEN, "invalid character in header")            \
   XX(INVALID_CONTENT_LENGTH,                                         \
      "invalid character in content-length header")                   \
+  XX(UNEXPECTED_CONTENT_LENGTH,                                      \
+     "unexpected content-length header")                             \
   XX(INVALID_CHUNK_SIZE,                                             \
      "invalid character in chunk size header")                       \
   XX(INVALID_CONSTANT, "invalid constant string")                    \
@@ -214,10 +217,11 @@ enum http_errno {
 struct http_parser {
   /** PRIVATE **/
   unsigned int type : 2;         /* enum http_parser_type */
-  unsigned int flags : 7;        /* F_* values from 'flags' enum; semi-public */
+  unsigned int flags : 8;        /* F_* values from 'flags' enum; semi-public */
   unsigned int state : 7;        /* enum state from http_parser.c */
-  unsigned int header_state : 8; /* enum header_state from http_parser.c */
-  unsigned int index : 8;        /* index into current matcher */
+  unsigned int header_state : 7; /* enum header_state from http_parser.c */
+  unsigned int index : 7;        /* index into current matcher */
+  unsigned int lenient_http_headers : 1;
 
   uint32_t nread;          /* # bytes read in various scenarios */
   uint64_t content_length; /* # bytes in body (0 if no Content-Length header) */
diff --git a/test.c b/test.c
index c63b8f0..da27896 100644
--- a/test.c
+++ b/test.c
@@ -2444,7 +2444,7 @@ upgrade_message_fix(char *body, const size_t nread, const size_t nmsgs, ...) {
   va_list ap;
   size_t i;
   size_t off = 0;
- 
+
   va_start(ap, nmsgs);
 
   for (i = 0; i < nmsgs; i++) {
@@ -3270,6 +3270,155 @@ test_simple (const char *buf, enum http_errno err_expected)
   }
 }
 
+void
+test_invalid_header_content (int req, const char* str)
+{
+  http_parser parser;
+  http_parser_init(&parser, req ? HTTP_REQUEST : HTTP_RESPONSE);
+  size_t parsed;
+  const char *buf;
+  buf = req ?
+    "GET / HTTP/1.1\r\n" :
+    "HTTP/1.1 200 OK\r\n";
+  parsed = http_parser_execute(&parser, &settings_null, buf, strlen(buf));
+  assert(parsed == strlen(buf));
+
+  buf = str;
+  size_t buflen = strlen(buf);
+
+  parsed = http_parser_execute(&parser, &settings_null, buf, buflen);
+  if (parsed != buflen) {
+    assert(HTTP_PARSER_ERRNO(&parser) == HPE_INVALID_HEADER_TOKEN);
+    return;
+  }
+
+  fprintf(stderr,
+          "\n*** Error expected but none in invalid header content test ***\n");
+  abort();
+}
+
+void
+test_invalid_header_field_content_error (int req)
+{
+  test_invalid_header_content(req, "Foo: F\01ailure");
+  test_invalid_header_content(req, "Foo: B\02ar");
+}
+
+void
+test_invalid_header_field (int req, const char* str)
+{
+  http_parser parser;
+  http_parser_init(&parser, req ? HTTP_REQUEST : HTTP_RESPONSE);
+  size_t parsed;
+  const char *buf;
+  buf = req ?
+    "GET / HTTP/1.1\r\n" :
+    "HTTP/1.1 200 OK\r\n";
+  parsed = http_parser_execute(&parser, &settings_null, buf, strlen(buf));
+  assert(parsed == strlen(buf));
+
+  buf = str;
+  size_t buflen = strlen(buf);
+
+  parsed = http_parser_execute(&parser, &settings_null, buf, buflen);
+  if (parsed != buflen) {
+    assert(HTTP_PARSER_ERRNO(&parser) == HPE_INVALID_HEADER_TOKEN);
+    return;
+  }
+
+  fprintf(stderr,
+          "\n*** Error expected but none in invalid header token test ***\n");
+  abort();
+}
+
+void
+test_invalid_header_field_token_error (int req)
+{
+  test_invalid_header_field(req, "Fo@: Failure");
+  test_invalid_header_field(req, "Foo\01\test: Bar");
+}
+
+void
+test_double_content_length_error (int req)
+{
+  http_parser parser;
+  http_parser_init(&parser, req ? HTTP_REQUEST : HTTP_RESPONSE);
+  size_t parsed;
+  const char *buf;
+  buf = req ?
+    "GET / HTTP/1.1\r\n" :
+    "HTTP/1.1 200 OK\r\n";
+  parsed = http_parser_execute(&parser, &settings_null, buf, strlen(buf));
+  assert(parsed == strlen(buf));
+
+  buf = "Content-Length: 0\r\nContent-Length: 1\r\n\r\n";
+  size_t buflen = strlen(buf);
+
+  parsed = http_parser_execute(&parser, &settings_null, buf, buflen);
+  if (parsed != buflen) {
+    assert(HTTP_PARSER_ERRNO(&parser) == HPE_MULTIPLE_CONTENT_LENGTH);
+    return;
+  }
+
+  fprintf(stderr,
+          "\n*** Error expected but none in double content-length test ***\n");
+  abort();
+}
+
+void
+test_chunked_content_length_error (int req)
+{
+  http_parser parser;
+  http_parser_init(&parser, req ? HTTP_REQUEST : HTTP_RESPONSE);
+  size_t parsed;
+  const char *buf;
+  buf = req ?
+    "GET / HTTP/1.1\r\n" :
+    "HTTP/1.1 200 OK\r\n";
+  parsed = http_parser_execute(&parser, &settings_null, buf, strlen(buf));
+  assert(parsed == strlen(buf));
+
+  buf = "Transfer-Encoding: chunked\r\nContent-Length: 1\r\n\r\n";
+  size_t buflen = strlen(buf);
+
+  parsed = http_parser_execute(&parser, &settings_null, buf, buflen);
+  if (parsed != buflen) {
+    assert(HTTP_PARSER_ERRNO(&parser) == HPE_CHUNKED_WITH_CONTENT_LENGTH);
+    return;
+  }
+
+  fprintf(stderr,
+          "\n*** Error expected but none in chunked content-length test ***\n");
+  abort();
+}
+
+void
+test_header_cr_no_lf_error (int req)
+{
+  http_parser parser;
+  http_parser_init(&parser, req ? HTTP_REQUEST : HTTP_RESPONSE);
+  size_t parsed;
+  const char *buf;
+  buf = req ?
+    "GET / HTTP/1.1\r\n" :
+    "HTTP/1.1 200 OK\r\n";
+  parsed = http_parser_execute(&parser, &settings_null, buf, strlen(buf));
+  assert(parsed == strlen(buf));
+
+  buf = "Foo: 1\rBar: 1\r\n\r\n";
+  size_t buflen = strlen(buf);
+
+  parsed = http_parser_execute(&parser, &settings_null, buf, buflen);
+  if (parsed != buflen) {
+    assert(HTTP_PARSER_ERRNO(&parser) == HPE_LF_EXPECTED);
+    return;
+  }
+
+  fprintf(stderr,
+          "\n*** Error expected but none in header whitespace test ***\n");
+  abort();
+}
+
 void
 test_header_overflow_error (int req)
 {
@@ -3696,6 +3845,18 @@ main (void)
   test_header_content_length_overflow_error();
   test_chunk_content_length_overflow_error();
 
+  //// HEADER FIELD CONDITIONS
+  test_double_content_length_error(HTTP_REQUEST);
+  test_chunked_content_length_error(HTTP_REQUEST);
+  test_header_cr_no_lf_error(HTTP_REQUEST);
+  test_invalid_header_field_token_error(HTTP_REQUEST);
+  test_invalid_header_field_content_error(HTTP_REQUEST);
+  test_double_content_length_error(HTTP_RESPONSE);
+  test_chunked_content_length_error(HTTP_RESPONSE);
+  test_header_cr_no_lf_error(HTTP_RESPONSE);
+  test_invalid_header_field_token_error(HTTP_RESPONSE);
+  test_invalid_header_field_content_error(HTTP_RESPONSE);
+
   //// RESPONSES
 
   for (i = 0; i < response_count; i++) {