diff --git a/defs/id.def b/defs/id.def
index f0e1db90dc..a35b5d55f9 100644
--- a/defs/id.def
+++ b/defs/id.def
@@ -60,7 +60,6 @@ firstline, predefined = __LINE__+1, %[\
   _                                                     UScore
 
   # MUST be successive
-  _0  NUMPARAM_0
   _1  NUMPARAM_1
   _2  NUMPARAM_2
   _3  NUMPARAM_3
diff --git a/parse.y b/parse.y
index 48dd44a197..14568d98c3 100644
--- a/parse.y
+++ b/parse.y
@@ -173,9 +173,16 @@ enum {
     NUMPARAM_MAX = 9,
 };
 
-#define NUMPARAM_ID_P(id) (is_local_id(id) && NUMPARAM_ID_TO_IDX(id) <= NUMPARAM_MAX)
-#define NUMPARAM_ID_TO_IDX(id) (unsigned int)(((id) >> ID_SCOPE_SHIFT) - tNUMPARAM_0)
-#define NUMPARAM_IDX_TO_ID(idx) TOKEN2LOCALID((tNUMPARAM_0 + (idx)))
+#define NUMPARAM_ID_P(id) numparam_id_p(id)
+#define NUMPARAM_ID_TO_IDX(id) (unsigned int)(((id) >> ID_SCOPE_SHIFT) - tNUMPARAM_1 + 1)
+#define NUMPARAM_IDX_TO_ID(idx) TOKEN2LOCALID((tNUMPARAM_1 + (idx) - 1))
+static int
+numparam_id_p(ID id)
+{
+    if (!is_local_id(id)) return 0;
+    unsigned int idx = NUMPARAM_ID_TO_IDX(id);
+    return idx > 0 && idx <= NUMPARAM_MAX;
+}
 
 #define DVARS_INHERIT ((void*)1)
 #define DVARS_TOPSCOPE NULL
diff --git a/test/ripper/test_parser_events.rb b/test/ripper/test_parser_events.rb
index 662ab3d7fe..4cb56f66f0 100644
--- a/test/ripper/test_parser_events.rb
+++ b/test/ripper/test_parser_events.rb
@@ -60,7 +60,6 @@ class TestRipper::ParserEvents < Test::Unit::TestCase
     assert_equal '[ref(true)]', parse('true')
     assert_equal '[vcall(_0)]', parse('_0')
     assert_equal '[vcall(_1)]', parse('_1')
-    assert_include parse('proc{_0}'), '[ref(_0)]'
     assert_include parse('proc{_1}'), '[ref(_1)]'
   end