diff --git a/ext/objspace/objspace.c b/ext/objspace/objspace.c
index ba755b1ad60f71..b12f5cb7c8c80e 100644
--- a/ext/objspace/objspace.c
+++ b/ext/objspace/objspace.c
@@ -295,28 +295,27 @@ size_t rb_sym_immortal_count(void);
 
 /*
  *  call-seq:
- *     ObjectSpace.count_symbols([result_hash]) -> hash
+ *     ObjectSpace.count_symbols(result_hash = nil) -> hash
  *
- *  Counts symbols for each Symbol type.
+ *  Returns a hash containing the number of objects for each Symbol type.
  *
- *  This method is only for MRI developers interested in performance and memory
- *  usage of Ruby programs.
+ *  The types of Symbols are the following:
  *
- *  If the optional argument, result_hash, is given, it is overwritten and
- *  returned. This is intended to avoid probe effect.
+ *  - +mortal_dynamic_symbol+: Symbols that are garbage collectable.
+ *  - +immortal_dynamic_symbol+: Symbols that are objects allocated from the
+ *    garbage collector, but are not garbage collectable.
+ *  - +immortal_static_symbol+: Symbols that are not allocated from the
+ *    garbage collector, and are thus not garbage collectable.
+ *  - +immortal_symbol+: the sum of +immortal_dynamic_symbol+ and +immortal_static_symbol+.
  *
- *  Note:
- *  The contents of the returned hash is implementation defined.
- *  It may be changed in future.
- *
- *  This method is only expected to work with C Ruby.
+ *  If the optional argument +result_hash+ is given, it is overwritten and
+ *  returned. This is intended to avoid the probe effect.
  *
- *  On this version of MRI, they have 3 types of Symbols (and 1 total counts).
+ *  This method is intended for developers interested in performance and memory
+ *  usage of Ruby programs. The contents of the returned hash is implementation
+ *  specific and may change in the future.
  *
- *   * mortal_dynamic_symbol: GC target symbols (collected by GC)
- *   * immortal_dynamic_symbol: Immortal symbols promoted from dynamic symbols (do not collected by GC)
- *   * immortal_static_symbol: Immortal symbols (do not collected by GC)
- *   * immortal_symbol: total immortal symbols (immortal_dynamic_symbol+immortal_static_symbol)
+ *  This method is only expected to work with C Ruby.
  */
 
 static VALUE
@@ -365,32 +364,22 @@ cto_i(VALUE v, void *data)
 
 /*
  *  call-seq:
- *     ObjectSpace.count_tdata_objects([result_hash]) -> hash
- *
- *  Counts objects for each +T_DATA+ type.
- *
- *  This method is only for MRI developers interested in performance and memory
- *  usage of Ruby programs.
+ *     ObjectSpace.count_tdata_objects(result_hash = nil) -> hash
  *
- *  It returns a hash as:
- *
- *	{RubyVM::InstructionSequence=>504, :parser=>5, :barrier=>6,
- *  	 :mutex=>6, Proc=>60, RubyVM::Env=>57, Mutex=>1, Encoding=>99,
- *  	 ThreadGroup=>1, Binding=>1, Thread=>1, RubyVM=>1, :iseq=>1,
- *  	 Random=>1, ARGF.class=>1, Data=>1, :autoload=>3, Time=>2}
- *  	# T_DATA objects existing at startup on r32276.
+ *  Returns a hash containing the number of objects for each +T_DATA+ type.
+ *  The keys are Class objects when the +T_DATA+ object has an associated class,
+ *  or Symbol objects of the name defined in the +rb_data_type_struct+ for internal
+ *  +T_DATA+ objects.
  *
- *  If the optional argument, result_hash, is given, it is overwritten and
- *  returned. This is intended to avoid probe effect.
+ *    ObjectSpace.count_tdata_objects
+ *    # => {RBS::Location => 39255, marshal_compat_table: 1, Encoding => 103, mutex: 1, ... }
  *
- *  The contents of the returned hash is implementation specific and may change
- *  in the future.
+ *  If the optional argument +result_hash+ is given, it is overwritten and
+ *  returned. This is intended to avoid the probe effect.
  *
- *  In this version, keys are Class object or Symbol object.
- *
- *  If object is kind of normal (accessible) object, the key is Class object.
- *  If object is not a kind of normal (internal) object, the key is symbol
- *  name, registered by rb_data_type_struct.
+ *  This method is intended for developers interested in performance and memory
+ *  usage of Ruby programs. The contents of the returned hash is implementation
+ *  specific and may change in the future.
  *
  *  This method is only expected to work with C Ruby.
  */
@@ -429,28 +418,22 @@ count_imemo_objects_i(VALUE v, void *data)
 
 /*
  *  call-seq:
- *     ObjectSpace.count_imemo_objects([result_hash]) -> hash
- *
- *  Counts objects for each +T_IMEMO+ type.
- *
- *  This method is only for MRI developers interested in performance and memory
- *  usage of Ruby programs.
- *
- *  It returns a hash as:
+ *     ObjectSpace.count_imemo_objects(result_hash = nil) -> hash
  *
- *       {:imemo_ifunc=>8,
- *        :imemo_svar=>7,
- *        :imemo_cref=>509,
- *        :imemo_memo=>1,
- *        :imemo_throw_data=>1}
+ *  Returns a hash containing the number of objects for each +T_IMEMO+ type.
+ *  The keys are Symbol objects of the +T_IMEMO+ type name.
+ *  +T_IMEMO+ objects are Ruby internal objects that are not visible to Ruby
+ *  programs.
  *
- *  If the optional argument, result_hash, is given, it is overwritten and
- *  returned. This is intended to avoid probe effect.
+ *    ObjectSpace.count_imemo_objects
+ *    # => {imemo_callcache: 5482, imemo_constcache: 1258, imemo_ment: 13906, ... }
  *
- *  The contents of the returned hash is implementation specific and may change
- *  in the future.
+ *  If the optional argument +result_hash+ is given, it is overwritten and
+ *  returned. This is intended to avoid the probe effect.
  *
- *  In this version, keys are symbol objects.
+ *  This method is intended for developers interested in performance and memory
+ *  usage of Ruby programs. The contents of the returned hash is implementation
+ *  specific and may change in the future.
  *
  *  This method is only expected to work with C Ruby.
  */
diff --git a/prism/prism.c b/prism/prism.c
index 1a8cdf7568fe98..b36a6da20493ba 100644
--- a/prism/prism.c
+++ b/prism/prism.c
@@ -3962,9 +3962,13 @@ pm_float_node_rational_create(pm_parser_t *parser, const pm_token_t *token) {
     memcpy(digits + (point - start), point + 1, (unsigned long) (end - point - 1));
     pm_integer_parse(&node->numerator, PM_INTEGER_BASE_DEFAULT, digits, digits + length - 1);
 
+    size_t fract_length = 0;
+    for (const uint8_t *fract = point; fract < end; ++fract) {
+        if (*fract != '_') ++fract_length;
+    }
     digits[0] = '1';
-    if (end - point > 1) memset(digits + 1, '0', (size_t) (end - point - 1));
-    pm_integer_parse(&node->denominator, PM_INTEGER_BASE_DEFAULT, digits, digits + (end - point));
+    if (fract_length > 1) memset(digits + 1, '0', fract_length - 1);
+    pm_integer_parse(&node->denominator, PM_INTEGER_BASE_DEFAULT, digits, digits + fract_length);
     xfree(digits);
 
     pm_integers_reduce(&node->numerator, &node->denominator);
diff --git a/test/prism/result/numeric_value_test.rb b/test/prism/result/numeric_value_test.rb
index 5c89230a1fee41..0207fa6a864917 100644
--- a/test/prism/result/numeric_value_test.rb
+++ b/test/prism/result/numeric_value_test.rb
@@ -6,16 +6,27 @@ module Prism
   class NumericValueTest < TestCase
     def test_numeric_value
       assert_equal 123, Prism.parse_statement("123").value
+      assert_equal 123, Prism.parse_statement("1_23").value
       assert_equal 3.14, Prism.parse_statement("3.14").value
+      assert_equal 3.14, Prism.parse_statement("3.1_4").value
       assert_equal 42i, Prism.parse_statement("42i").value
+      assert_equal 42i, Prism.parse_statement("4_2i").value
       assert_equal 42.1ri, Prism.parse_statement("42.1ri").value
+      assert_equal 42.1ri, Prism.parse_statement("42.1_0ri").value
       assert_equal 3.14i, Prism.parse_statement("3.14i").value
+      assert_equal 3.14i, Prism.parse_statement("3.1_4i").value
       assert_equal 42r, Prism.parse_statement("42r").value
+      assert_equal 42r, Prism.parse_statement("4_2r").value
       assert_equal 0.5r, Prism.parse_statement("0.5r").value
+      assert_equal 0.5r, Prism.parse_statement("0.5_0r").value
       assert_equal 42ri, Prism.parse_statement("42ri").value
+      assert_equal 42ri, Prism.parse_statement("4_2ri").value
       assert_equal 0.5ri, Prism.parse_statement("0.5ri").value
+      assert_equal 0.5ri, Prism.parse_statement("0.5_0ri").value
       assert_equal 0xFFr, Prism.parse_statement("0xFFr").value
+      assert_equal 0xFFr, Prism.parse_statement("0xF_Fr").value
       assert_equal 0xFFri, Prism.parse_statement("0xFFri").value
+      assert_equal 0xFFri, Prism.parse_statement("0xF_Fri").value
     end
   end
 end
diff --git a/test/ruby/test_literal.rb b/test/ruby/test_literal.rb
index dbff3c4734275d..cff888d4b3a5d4 100644
--- a/test/ruby/test_literal.rb
+++ b/test/ruby/test_literal.rb
@@ -682,6 +682,11 @@ def test_float
     $VERBOSE = verbose_bak
   end
 
+  def test_rational_float
+    assert_equal(12, 0.12r * 100)
+    assert_equal(12, 0.1_2r * 100)
+  end
+
   def test_symbol_list
     assert_equal([:foo, :bar], %i[foo bar])
     assert_equal([:"\"foo"], %i["foo])