diff --git a/lib/_http_outgoing.js b/lib/_http_outgoing.js
index a7467168c5899f..2b0b158721f562 100644
--- a/lib/_http_outgoing.js
+++ b/lib/_http_outgoing.js
@@ -315,6 +315,7 @@ function storeHeader(self, state, field, value) {
       'Header name must be a valid HTTP Token ["' + field + '"]');
   }
   if (common._checkInvalidHeaderChar(value) === true) {
+    debug('Header "%s" contains invalid characters', field);
     throw new TypeError('The header content contains invalid characters');
   }
   state.messageHeader += field + ': ' + escapeHeaderValue(value) + CRLF;
@@ -355,6 +356,7 @@ OutgoingMessage.prototype.setHeader = function(name, value) {
   if (this._header)
     throw new Error('Can\'t set headers after they are sent.');
   if (common._checkInvalidHeaderChar(value) === true) {
+    debug('Header "%s" contains invalid characters', name);
     throw new TypeError('The header content contains invalid characters');
   }
   if (this._headers === null)
@@ -532,6 +534,7 @@ OutgoingMessage.prototype.addTrailers = function(headers) {
         'Trailer name must be a valid HTTP Token ["' + field + '"]');
     }
     if (common._checkInvalidHeaderChar(value) === true) {
+      debug('Trailer "%s" contains invalid characters', field);
       throw new TypeError('The header content contains invalid characters');
     }
     this._trailer += field + ': ' + escapeHeaderValue(value) + CRLF;