diff --git a/src/http/modules/ngx_http_fastcgi_module.c b/src/http/modules/ngx_http_fastcgi_module.c
index 5191880..69ac0f7 100644
--- a/src/http/modules/ngx_http_fastcgi_module.c
+++ b/src/http/modules/ngx_http_fastcgi_module.c
@@ -2019,10 +2019,12 @@
                 break;
             }
 
-            /* there was error while a header line parsing */
+            /* rc == NGX_HTTP_PARSE_INVALID_HEADER */
 
-            ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
-                          "upstream sent invalid header");
+            ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
+                          "upstream sent invalid header: \"%*s\\x%02xd...\"",
+                          r->header_end - r->header_name_start,
+                          r->header_name_start, *r->header_end);
 
             return NGX_HTTP_UPSTREAM_INVALID_HEADER;
         }
diff --git a/src/http/modules/ngx_http_proxy_module.c b/src/http/modules/ngx_http_proxy_module.c
index d82f5ea..368297e 100644
--- a/src/http/modules/ngx_http_proxy_module.c
+++ b/src/http/modules/ngx_http_proxy_module.c
@@ -2019,10 +2019,12 @@
             return NGX_AGAIN;
         }
 
-        /* there was error while a header line parsing */
+        /* rc == NGX_HTTP_PARSE_INVALID_HEADER */
 
-        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
-                      "upstream sent invalid header");
+        ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
+                      "upstream sent invalid header: \"%*s\\x%02xd...\"",
+                      r->header_end - r->header_name_start,
+                      r->header_name_start, *r->header_end);
 
         return NGX_HTTP_UPSTREAM_INVALID_HEADER;
     }
diff --git a/src/http/modules/ngx_http_scgi_module.c b/src/http/modules/ngx_http_scgi_module.c
index 600999c..570713d 100644
--- a/src/http/modules/ngx_http_scgi_module.c
+++ b/src/http/modules/ngx_http_scgi_module.c
@@ -1140,10 +1140,12 @@
             return NGX_AGAIN;
         }
 
-        /* there was error while a header line parsing */
+        /* rc == NGX_HTTP_PARSE_INVALID_HEADER */
 
-        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
-                      "upstream sent invalid header");
+        ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
+                      "upstream sent invalid header: \"%*s\\x%02xd...\"",
+                      r->header_end - r->header_name_start,
+                      r->header_name_start, *r->header_end);
 
         return NGX_HTTP_UPSTREAM_INVALID_HEADER;
     }
diff --git a/src/http/modules/ngx_http_uwsgi_module.c b/src/http/modules/ngx_http_uwsgi_module.c
index 655be98..40a06c7 100644
--- a/src/http/modules/ngx_http_uwsgi_module.c
+++ b/src/http/modules/ngx_http_uwsgi_module.c
@@ -1361,10 +1361,12 @@
             return NGX_AGAIN;
         }
 
-        /* there was error while a header line parsing */
+        /* rc == NGX_HTTP_PARSE_INVALID_HEADER */
 
-        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
-                      "upstream sent invalid header");
+        ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
+                      "upstream sent invalid header: \"%*s\\x%02xd...\"",
+                      r->header_end - r->header_name_start,
+                      r->header_name_start, *r->header_end);
 
         return NGX_HTTP_UPSTREAM_INVALID_HEADER;
     }
diff --git a/src/http/ngx_http_parse.c b/src/http/ngx_http_parse.c
index 6af326d..6460da2 100644
--- a/src/http/ngx_http_parse.c
+++ b/src/http/ngx_http_parse.c
@@ -894,6 +894,7 @@
                 }
 
                 if (ch <= 0x20 || ch == 0x7f || ch == ':') {
+                    r->header_end = p;
                     return NGX_HTTP_PARSE_INVALID_HEADER;
                 }
 
@@ -962,6 +963,7 @@
             }
 
             if (ch <= 0x20 || ch == 0x7f) {
+                r->header_end = p;
                 return NGX_HTTP_PARSE_INVALID_HEADER;
             }
 
@@ -984,6 +986,7 @@
                 r->header_end = p;
                 goto done;
             case '\0':
+                r->header_end = p;
                 return NGX_HTTP_PARSE_INVALID_HEADER;
             default:
                 r->header_start = p;
@@ -1007,6 +1010,7 @@
                 r->header_end = p;
                 goto done;
             case '\0':
+                r->header_end = p;
                 return NGX_HTTP_PARSE_INVALID_HEADER;
             }
             break;
@@ -1022,6 +1026,7 @@
             case LF:
                 goto done;
             case '\0':
+                r->header_end = p;
                 return NGX_HTTP_PARSE_INVALID_HEADER;
             default:
                 state = sw_value;
diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index 7956610..2e7c30f 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -1522,7 +1522,9 @@
         /* rc == NGX_HTTP_PARSE_INVALID_HEADER */
 
         ngx_log_error(NGX_LOG_INFO, c->log, 0,
-                      "client sent invalid header line");
+                      "client sent invalid header line: \"%*s\\x%02xd...\"",
+                      r->header_end - r->header_name_start,
+                      r->header_name_start, *r->header_end);
 
         ngx_http_finalize_request(r, NGX_HTTP_BAD_REQUEST);
         break;