diff --git a/assets/parser.rs.erb b/assets/parser.rs.erb
index 79c727b..3fc5e0e 100644
--- a/assets/parser.rs.erb
+++ b/assets/parser.rs.erb
@@ -26,13 +26,24 @@
  *************************************************************************/
 
 /* Result codes. */
-pub const P_SUCCESS: usize = 0;
-pub const P_DECODE_ERROR: usize = 1;
-pub const P_UNEXPECTED_INPUT: usize = 2;
-pub const P_UNEXPECTED_TOKEN: usize = 3;
-pub const P_DROP: usize = 4;
-pub const P_EOF: usize = 5;
-pub const P_USER_TERMINATED: usize = 6;
+pub const <%= @grammar.prefix.upcase %>SUCCESS: usize = 0;
+pub const <%= @grammar.prefix.upcase %>DECODE_ERROR: usize = 1;
+pub const <%= @grammar.prefix.upcase %>UNEXPECTED_INPUT: usize = 2;
+pub const <%= @grammar.prefix.upcase %>UNEXPECTED_TOKEN: usize = 3;
+pub const <%= @grammar.prefix.upcase %>DROP: usize = 4;
+pub const <%= @grammar.prefix.upcase %>EOF: usize = 5;
+pub const <%= @grammar.prefix.upcase %>USER_TERMINATED: usize = 6;
+<% if @grammar.prefix.upcase != "P_" %>
+
+/* Internal result code aliases used by the generated implementation below. */
+const P_SUCCESS: usize = 0;
+const P_DECODE_ERROR: usize = 1;
+const P_UNEXPECTED_INPUT: usize = 2;
+const P_UNEXPECTED_TOKEN: usize = 3;
+const P_DROP: usize = 4;
+const P_EOF: usize = 5;
+const P_USER_TERMINATED: usize = 6;
+<% end %>
 
 /** Token type. */
 pub type <%= @grammar.prefix %>token_t = <%= get_type_for(@grammar.terminate_token_id) %>;
diff --git a/spec/test_multiple_parsers.rs b/spec/test_multiple_parsers.rs
index b589f90..c418cbf 100644
--- a/spec/test_multiple_parsers.rs
+++ b/spec/test_multiple_parsers.rs
@@ -3,10 +3,10 @@ use testparsermyp2 as m2;
 
 fn main() {
     let mut context1 = m1::myp1_context_new(b"a\n1");
-    assert_eq!(m1::P_SUCCESS, m1::myp1_parse(&mut context1));
+    assert_eq!(m1::MYP1_SUCCESS, m1::myp1_parse(&mut context1));
     m1::myp1_context_delete(context1);
 
     let mut context2 = m2::myp2_context_new(b"bcb");
-    assert_eq!(m2::P_SUCCESS, m2::myp2_parse(&mut context2));
+    assert_eq!(m2::MYP2_SUCCESS, m2::myp2_parse(&mut context2));
     m2::myp2_context_delete(context2);
 }