diff --git a/mrbgems/mruby-range-ext/src/range.c b/mrbgems/mruby-range-ext/src/range.c
index babc0d931..b8fec473b 100644
--- a/mrbgems/mruby-range-ext/src/range.c
+++ b/mrbgems/mruby-range-ext/src/range.c
@@ -111,7 +111,13 @@ range_size(mrb_state *mrb, mrb_value range)
   mrb_value beg = RANGE_BEG(r);
   mrb_value end = RANGE_END(r);
 
-  if ((mrb_integer_p(beg) || mrb_float_p(beg)) && mrb_nil_p(end)) {
+  if (mrb_float_p(beg)) {
+    mrb_raise(mrb, E_TYPE_ERROR, "can't iterate from Float");
+  }
+  if (mrb_nil_p(beg)) {
+    mrb_raise(mrb, E_TYPE_ERROR, "can't iterate from nil");
+  }
+  if (mrb_integer_p(beg) && mrb_nil_p(end)) {
     return mrb_float_value(mrb, INFINITY);
   }
 
@@ -167,6 +173,9 @@ range_size(mrb_state *mrb, mrb_value range)
 
   mrb_value beg = RANGE_BEG(r);
   mrb_value end = RANGE_END(r);
+  if (mrb_nil_p(beg)) {
+    mrb_raise(mrb, E_TYPE_ERROR, "can't iterate from nil");
+  }
   if (mrb_integer_p(beg) && mrb_nil_p(end)) {
     return mrb_nil_value();
   }
diff --git a/mrbgems/mruby-range-ext/test/range.rb b/mrbgems/mruby-range-ext/test/range.rb
index d37712926..96ced593e 100644
--- a/mrbgems/mruby-range-ext/test/range.rb
+++ b/mrbgems/mruby-range-ext/test/range.rb
@@ -55,13 +55,10 @@ assert('Range#size') do
   skip unless Object.const_defined?(:Float)
   assert_equal 6, (1...6.3).size
   assert_equal 5, (1...6.0).size
-  assert_equal 5, (1.1...6).size
-  assert_equal 15, (1.0..15.9).size
   assert_equal Float::INFINITY, (0..Float::INFINITY).size
 
   assert_equal Float::INFINITY, (1..).size
   assert_equal Float::INFINITY, (1...).size
-  assert_equal Float::INFINITY, (1.0..).size
 end
 
 assert('Range#max') do