diff --git a/internal.h b/internal.h
index 6a7f039cd0..dd7d09a6e3 100644
--- a/internal.h
+++ b/internal.h
@@ -1178,6 +1178,7 @@ VALUE rb_int_cmp(VALUE x, VALUE y);
 VALUE rb_int_equal(VALUE x, VALUE y);
 VALUE rb_int_divmod(VALUE x, VALUE y);
 VALUE rb_int_and(VALUE x, VALUE y);
+VALUE rb_int_lshift(VALUE x, VALUE y);
 
 #if USE_FLONUM
 #define RUBY_BIT_ROTL(v, n) (((v) << (n)) | ((v) >> ((sizeof(v) * 8) - n)))
diff --git a/numeric.c b/numeric.c
index e0d6358932..590bec72e1 100644
--- a/numeric.c
+++ b/numeric.c
@@ -4390,7 +4390,7 @@ fix_lshift(long val, unsigned long width)
     return LONG2NUM(val);
 }
 
-static VALUE
+VALUE
 rb_int_lshift(VALUE x, VALUE y)
 {
     if (FIXNUM_P(x)) {
diff --git a/rational.c b/rational.c
index 67752ff961..c7f66c4767 100644
--- a/rational.c
+++ b/rational.c
@@ -2071,14 +2071,17 @@ float_to_r(VALUE self)
 	long ln = FIX2LONG(n);
 
 	if (ln == 0)
-	    return f_to_r(f);
+	    return rb_rational_new1(f);
 	if (ln > 0)
-	    return f_to_r(f_lshift(f, n));
+	    return rb_rational_new1(rb_int_lshift(f, n));
 	ln = -ln;
-	return rb_rational_new2(f, f_lshift(ONE, INT2FIX(ln)));
+	return rb_rational_new2(f, rb_int_lshift(ONE, INT2FIX(ln)));
     }
 #else
-    return f_to_r(f_mul(f, f_expt(INT2FIX(FLT_RADIX), n)));
+    f = rb_int_mul(f, rb_int_pow(INT2FIX(FLT_RADIX), n));
+    if (RB_TYPE_P(f, T_RATIONAL))
+	return f;
+    return rb_rational_new1(f);
 #endif
 }