diff --git a/defs/id.def b/defs/id.def
index 90d2e84074..42386e5f36 100644
--- a/defs/id.def
+++ b/defs/id.def
@@ -35,6 +35,7 @@ firstline, predefined = __LINE__+1, %[\
   to_io
   to_a
   to_s
+  to_i
 
   _                                                     UScore
   "/*NULL*/"                                            NULL
diff --git a/numeric.c b/numeric.c
index 35aa8e93c9..34abd1d90c 100644
--- a/numeric.c
+++ b/numeric.c
@@ -109,7 +109,8 @@ static VALUE fix_uminus(VALUE num);
 static VALUE fix_mul(VALUE x, VALUE y);
 static VALUE int_pow(long x, unsigned long y);
 
-static ID id_coerce, id_to_i, id_div;
+static ID id_coerce, id_div;
+#define id_to_i idTo_i
 #define id_eq  idEq
 #define id_cmp idCmp
 
@@ -3981,7 +3982,6 @@ Init_Numeric(void)
     _control87(_control87(0,0),0x1FFF);
 #endif
     id_coerce = rb_intern("coerce");
-    id_to_i = rb_intern("to_i");
     id_div = rb_intern("div");
 
     rb_eZeroDivError = rb_define_class("ZeroDivisionError", rb_eStandardError);
diff --git a/object.c b/object.c
index 4f360a7906..582e2e2121 100644
--- a/object.c
+++ b/object.c
@@ -2559,6 +2559,7 @@ static const struct conv_method_tbl {
     M(io),
     M(a),
     M(s),
+    M(i),
 #undef M
 };
 #define IMPLICIT_CONVERSIONS 7