diff --git a/src/detail/header.cpp b/src/detail/header.cpp
index 79637a91..b436bae1 100644
--- a/src/detail/header.cpp
+++ b/src/detail/header.cpp
@@ -1125,10 +1125,12 @@ parse_start_line(
             it, end, request_line_rule);
         if(! rv)
         {
-            ec = rv.error();
-            if( ec == system::error_code(grammar::error::need_more) &&
-                new_size == lim.max_start_line)
+            if( rv.error() != grammar::error::need_more )
+                ec = rv.error();
+            else if( new_size == lim.max_start_line )
                 ec = error::start_line_limit;
+            else
+                ec = error::need_data;
             return;
         }
         // method
@@ -1164,10 +1166,12 @@ parse_start_line(
             it, end, status_line_rule);
         if(! rv)
         {
-            ec = rv.error();
-            if( ec == system::error_code(grammar::error::need_more) &&
-                new_size == lim.max_start_line)
+            if( rv.error() != grammar::error::need_more )
+                ec = rv.error();
+            else if( new_size == lim.max_start_line )
                 ec = error::start_line_limit;
+            else
+                ec = error::need_data;
             return;
         }
         // version
@@ -1216,19 +1220,20 @@ parse_field(
         it, end, field_rule);
     if(rv.has_error())
     {
-        ec = rv.error();
-        if(ec == system::error_code(grammar::error::end_of_range))
+        if(rv.error() == grammar::error::end_of_range)
         {
             // final CRLF
             h.size = static_cast<
                 header::offset_type>(it - h.cbuf);
+            ec = error::end_of_message;
             return;
         }
-        if( ec == system::error_code(grammar::error::need_more) &&
-            new_size == lim.max_field)
-        {
+        if( rv.error() != grammar::error::need_more )
+            ec = rv.error();
+        else if( new_size == lim.max_field )
             ec = error::field_size_limit;
-        }
+        else
+            ec = error::need_data;
         return;
     }
     if(h.count >= lim.max_fields)
@@ -1285,7 +1290,7 @@ parse(
             *this, lim, new_size, ec);
         if(ec)
         {
-            if( ec == system::error_code(grammar::error::need_more) &&
+            if( ec == error::need_data &&
                 new_size == lim.max_fields)
             {
                 ec = error::headers_limit;
@@ -1299,7 +1304,7 @@ parse(
             *this, lim, new_size, ec);
         if(ec)
         {
-            if( ec == system::error_code(grammar::error::need_more) &&
+            if( ec == error::need_data &&
                 new_size == lim.max_size)
             {
                 ec = error::headers_limit;
@@ -1308,7 +1313,7 @@ parse(
             break;
         }
     }
-    if(ec == system::error_code(grammar::error::end_of_range))
+    if(ec == error::end_of_message)
         ec = {};
 }
 
diff --git a/src/error.cpp b/src/error.cpp
index 2f7aca46..e2ba5719 100644
--- a/src/error.cpp
+++ b/src/error.cpp
@@ -102,14 +102,8 @@ equivalent(
     {
     case condition::invalid_payload:
         return (ec == error::bad_payload);
-
     case condition::need_more_input:
-        if( ec == system::error_code(
-                urls::grammar::error::need_more) ||
-            ec == error::need_data )
-            return true;
-        break;
-
+        return ec == error::need_data;
     default:
         break;
     }
diff --git a/src/fields_base.cpp b/src/fields_base.cpp
index af1bb90f..dc4b16be 100644
--- a/src/fields_base.cpp
+++ b/src/fields_base.cpp
@@ -72,7 +72,7 @@ verify_field_value(
         grammar::parse(it, end, detail::field_value_rule);
     if( rv.has_error() )
     {
-        if( rv.error() == condition::need_more_input )
+        if( rv.error() == grammar::error::need_more )
             return error::bad_field_value;
         return rv.error();
     }
diff --git a/test/unit/error.cpp b/test/unit/error.cpp
index 5370028a..6fb55466 100644
--- a/test/unit/error.cpp
+++ b/test/unit/error.cpp
@@ -9,7 +9,6 @@
 
 // Test that header file is self-contained.
 #include <boost/http/error.hpp>
-#include <boost/url/grammar/error.hpp>
 
 #include <memory>
 
@@ -111,8 +110,7 @@ class error_test
 
         check(n,
             condition::need_more_input,
-            system::error_code(
-                urls::grammar::error::need_more));
+            error::need_data);
         check(n,
              condition::invalid_payload,
              error::bad_payload);