diff --git a/range.c b/range.c
index e9073e53c40eb3..a6bf0fca51eb35 100644
--- a/range.c
+++ b/range.c
@@ -827,7 +827,12 @@ sym_each_i(VALUE v, VALUE arg)
  *    (1..4).size      # => 4
  *    (1...4).size     # => 3
  *    (1..).size       # => Infinity
- *    ('a'..'z').size  #=> nil
+ *    ('a'..'z').size  # => nil
+ *
+ *  If +self+ is not iterable, raises an exception:
+ *
+ *    (0.5..2.5).size  # TypeError
+ *    (..1).size       # TypeError
  *
  *  Related: Range#count.
  */
@@ -836,7 +841,8 @@ static VALUE
 range_size(VALUE range)
 {
     VALUE b = RANGE_BEG(range), e = RANGE_END(range);
-    if (rb_obj_is_kind_of(b, rb_cNumeric)) {
+
+    if (RB_INTEGER_TYPE_P(b)) {
         if (rb_obj_is_kind_of(e, rb_cNumeric)) {
             return ruby_num_interval_step_size(b, e, INT2FIX(1), EXCL(range));
         }
@@ -844,10 +850,10 @@ range_size(VALUE range)
             return DBL2NUM(HUGE_VAL);
         }
     }
-    else if (NIL_P(b)) {
-        if (rb_obj_is_kind_of(e, rb_cNumeric)) {
-            return DBL2NUM(HUGE_VAL);
-        }
+
+    if (!discrete_object_p(b)) {
+        rb_raise(rb_eTypeError, "can't iterate from %s",
+                 rb_obj_classname(b));
     }
 
     return Qnil;
diff --git a/spec/ruby/core/range/size_spec.rb b/spec/ruby/core/range/size_spec.rb
index 81ea5a3846ab37..a1fe3ce17de3d7 100644
--- a/spec/ruby/core/range/size_spec.rb
+++ b/spec/ruby/core/range/size_spec.rb
@@ -4,34 +4,22 @@
   it "returns the number of elements in the range" do
     (1..16).size.should == 16
     (1...16).size.should == 15
-
-    (1.0..16.0).size.should == 16
-    (1.0...16.0).size.should == 15
-    (1.0..15.9).size.should == 15
-    (1.1..16.0).size.should == 15
-    (1.1..15.9).size.should == 15
   end
 
   it "returns 0 if last is less than first" do
     (16..0).size.should == 0
-    (16.0..0.0).size.should == 0
-    (Float::INFINITY..0).size.should == 0
   end
 
   it 'returns Float::INFINITY for increasing, infinite ranges' do
     (0..Float::INFINITY).size.should == Float::INFINITY
-    (-Float::INFINITY..0).size.should == Float::INFINITY
-    (-Float::INFINITY..Float::INFINITY).size.should == Float::INFINITY
   end
 
   it 'returns Float::INFINITY for endless ranges if the start is numeric' do
     eval("(1..)").size.should == Float::INFINITY
-    eval("(0.5...)").size.should == Float::INFINITY
   end
 
   it 'returns nil for endless ranges if the start is not numeric' do
     eval("('z'..)").size.should == nil
-    eval("([]...)").size.should == nil
   end
 
   ruby_version_is ""..."3.2" do
@@ -43,7 +31,7 @@
     end
   end
 
-  ruby_version_is "3.2" do
+  ruby_version_is "3.2"..."3.4" do
     it 'returns Float::INFINITY for all beginless ranges if the end is numeric' do
       (..1).size.should == Float::INFINITY
       (...0.5).size.should == Float::INFINITY
@@ -58,6 +46,54 @@
     end
   end
 
+  ruby_version_is ""..."3.4" do
+    it "returns the number of elements in the range" do
+      (1.0..16.0).size.should == 16
+      (1.0...16.0).size.should == 15
+      (1.0..15.9).size.should == 15
+      (1.1..16.0).size.should == 15
+      (1.1..15.9).size.should == 15
+    end
+
+    it "returns 0 if last is less than first" do
+      (16.0..0.0).size.should == 0
+      (Float::INFINITY..0).size.should == 0
+    end
+
+    it 'returns Float::INFINITY for increasing, infinite ranges' do
+      (-Float::INFINITY..0).size.should == Float::INFINITY
+      (-Float::INFINITY..Float::INFINITY).size.should == Float::INFINITY
+    end
+
+    it 'returns Float::INFINITY for endless ranges if the start is numeric' do
+      eval("(0.5...)").size.should == Float::INFINITY
+    end
+
+    it 'returns nil for endless ranges if the start is not numeric' do
+      eval("([]...)").size.should == nil
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it 'raises TypeError if a range is not iterable' do
+      -> { (1.0..16.0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (1.0...16.0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (1.0..15.9).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (1.1..16.0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (1.1..15.9).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (16.0..0.0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (Float::INFINITY..0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (-Float::INFINITY..0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (-Float::INFINITY..Float::INFINITY).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (..1).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (...0.5).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (..nil).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (...'o').size }.should raise_error(TypeError, /can't iterate from/)
+      -> { eval("(0.5...)").size }.should raise_error(TypeError, /can't iterate from/)
+      -> { eval("([]...)").size }.should raise_error(TypeError, /can't iterate from/)
+    end
+  end
+
   it "returns nil if first and last are not Numeric" do
     (:a..:z).size.should be_nil
     ('a'..'z').size.should be_nil
diff --git a/test/ruby/test_range.rb b/test/ruby/test_range.rb
index 2aa69dc6a49e47..84b3b205f03343 100644
--- a/test/ruby/test_range.rb
+++ b/test/ruby/test_range.rb
@@ -983,26 +983,38 @@ def test_comparison_when_recursive
   end
 
   def test_size
-    assert_equal 42, (1..42).size
-    assert_equal 41, (1...42).size
-    assert_equal 6, (1...6.3).size
-    assert_equal 5, (1.1...6).size
-    assert_equal 3, (1..3r).size
-    assert_equal 2, (1...3r).size
-    assert_equal 3, (1..3.1r).size
-    assert_equal 3, (1...3.1r).size
-    assert_equal 42, (1..42).each.size
+    Enumerator.product([:to_i, :to_f, :to_r].repeated_permutation(2), [1, 10], [5, 5.5], [true, false]) do |(m1, m2), beg, ende, exclude_end|
+      r = Range.new(beg.send(m1), ende.send(m2), exclude_end)
+      iterable = true
+      yielded = []
+      begin
+        r.each { yielded << _1 }
+      rescue TypeError
+        iterable = false
+      end
+
+      if iterable
+        assert_equal(yielded.size, r.size, "failed on #{r}")
+        assert_equal(yielded.size, r.each.size, "failed on #{r}")
+      else
+        assert_raise(TypeError, "failed on #{r}") { r.size }
+        assert_raise(TypeError, "failed on #{r}") { r.each.size }
+      end
+    end
+
     assert_nil ("a"..."z").size
-    assert_nil ("a"...).size
-    assert_nil (..."z").size    # [Bug #18983]
-    assert_nil (nil...nil).size # [Bug #18983]
-
-    assert_equal Float::INFINITY, (1...).size
-    assert_equal Float::INFINITY, (1.0...).size
-    assert_equal Float::INFINITY, (...1).size
-    assert_equal Float::INFINITY, (...1.0).size
-    assert_nil ("a"...).size
-    assert_nil (..."z").size
+
+    assert_equal Float::INFINITY, (1..).size
+    assert_raise(TypeError) { (1.0..).size }
+    assert_raise(TypeError) { (1r..).size }
+    assert_nil ("a"..).size
+
+    assert_raise(TypeError) { (..1).size }
+    assert_raise(TypeError) { (..1.0).size }
+    assert_raise(TypeError) { (..1r).size }
+    assert_raise(TypeError) { (..'z').size }
+
+    assert_raise(TypeError) { (nil...nil).size }
   end
 
   def test_bsearch_typechecks_return_values