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

index 67543a4..19efc6d 100644

--- a/src/HttpHeader.cc

+++ b/src/HttpHeader.cc

@@ -445,18 +445,6 @@ HttpHeader::parse(const char *header_start, size_t hdrLen)

             return 0;

         }

-        if (e->id == Http::HdrType::OTHER && stringHasWhitespace(e->name.termedBuf())) {

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

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

-

-            if (!Config.onoff.relaxed_header_parser) {

-                delete e;

-                PROF_stop(HttpHeaderParse);

-                clean();

-                return 0;

-            }

-        }

-

         addEntry(e);

     }

@@ -1451,6 +1439,20 @@ HttpHeaderEntry::parse(const char *field_start, const char *field_end, const htt

         }

     }

+    /* 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-field_start) << "'");