diff --git a/src/HttpHeader.cc b/src/HttpHeader.cc

index ef60c02..ce55a6f 100644

--- a/src/HttpHeader.cc

+++ b/src/HttpHeader.cc

@@ -12,6 +12,7 @@

 #include "base64.h"

 #include "globals.h"

 #include "http/ContentLengthInterpreter.h"

+#include "base/CharacterSet.h"

 #include "HttpHdrCc.h"

 #include "HttpHdrContRange.h"

 #include "HttpHdrSc.h"

@@ -707,18 +708,6 @@ HttpHeader::parse(const char *header_start, const char *header_end)

             return 0;

         }

-

-        if (e->id == HDR_OTHER && stringHasWhitespace(e->name.termedBuf())) {

-            debugs(55, warnOnError, "WARNING: found whitespace in HTTP header name {" <<

-                   getStringPrefix(field_start, field_end) << "}");

-

-            if (!Config.onoff.relaxed_header_parser) {

-                delete e;

-                PROF_stop(HttpHeaderParse);

-                return reset();

-            }

-        }

-

         addEntry(e);

     }

@@ -1653,6 +1642,20 @@ HttpHeaderEntry::parse(const char *field_start, const char *field_end)

             return NULL;

     }

+    /* RFC 7230 section 3.2:

+     *

+     *  header-field   = field-name ":" OWS field-value OWS

+     *  field-name     = token

+     *  token          = 1*TCHAR

+     */

+    for (const char *pos = field_start; pos < (field_start+name_len); ++pos) {

+        if (!CharacterSet::TCHAR[*pos]) {

+            debugs(55, 2, "found header with invalid characters in " <<

+                   Raw("field-name", field_start, min(name_len,100)) << "...");

+            return nullptr;

+        }

+    }

+

     /* now we know we can parse it */

     debugs(55, 9, "parsing HttpHeaderEntry: near '" <<  getStringPrefix(field_start, field_end) << "'");