diff --git a/numeric.c b/numeric.c
index 345067c6a5..5564a6eceb 100644
--- a/numeric.c
+++ b/numeric.c
@@ -1829,20 +1829,24 @@ flo_prev_float(VALUE vx)
 VALUE
 rb_float_floor(VALUE num, int ndigits)
 {
-    double number, f;
+    double number;
     number = RFLOAT_VALUE(num);
     if (number == 0.0) {
 	return ndigits > 0 ? DBL2NUM(number) : INT2FIX(0);
     }
     if (ndigits > 0) {
 	int binexp;
+        double f, mul, res;
 	frexp(number, &binexp);
 	if (float_round_overflow(ndigits, binexp)) return num;
 	if (number > 0.0 && float_round_underflow(ndigits, binexp))
 	    return DBL2NUM(0.0);
 	f = pow(10, ndigits);
-	f = floor(number * f) / f;
-	return DBL2NUM(f);
+        mul = floor(number * f);
+        res = (mul + 1) / f;
+        if (res > number)
+            res = mul / f;
+        return DBL2NUM(res);
     }
     else {
 	num = dbl2ival(floor(number));
diff --git a/test/ruby/test_numeric.rb b/test/ruby/test_numeric.rb
index 066afc83a2..b5486d387c 100644
--- a/test/ruby/test_numeric.rb
+++ b/test/ruby/test_numeric.rb
@@ -229,6 +229,15 @@ class TestNumeric < Test::Unit::TestCase
     assert_equal(-1, a.truncate)
   end
 
+  def test_floor_ceil_ndigits
+    bug17183 = "[ruby-core:100090]"
+    f = 291.4
+    31.times do |i|
+      assert_equal(291.4, f.floor(i+1), bug17183)
+      assert_equal(291.4, f.ceil(i+1), bug17183)
+    end
+  end
+
   def assert_step(expected, (from, *args), inf: false)
     kw = args.last.is_a?(Hash) ? args.pop : {}
     enum = from.step(*args, **kw)