diff --git a/doc/AST_FORMAT.md b/doc/AST_FORMAT.md
index ede684a1f..fcb1fe774 100644
--- a/doc/AST_FORMAT.md
+++ b/doc/AST_FORMAT.md
@@ -802,6 +802,31 @@ Format:
  ~~~~~~~~~~~~~~~~~ expression
 ~~~
 
+### "Endless" method
+
+Format:
+
+~~~
+(def_head :foo (args) (int 42))
+"def foo = 42"
+ ~~~ keyword
+     ~~~ name
+ ~~~~~~~~~~~~ expression
+~~~
+
+
+### "Endless" singleton method
+
+Format:
+
+~~~
+(defs_head (self) :foo (args) (int 42))
+"def self.foo = 42"
+ ~~~ keyword
+     ~~~ name
+ ~~~~~~~~~~~~ expression
+~~~
+
 ### Undefinition
 
 Format:
diff --git a/lib/parser/meta.rb b/lib/parser/meta.rb
index ab516aad5..22d1adb9f 100644
--- a/lib/parser/meta.rb
+++ b/lib/parser/meta.rb
@@ -16,7 +16,7 @@ module Meta
         op_asgn and_asgn ensure rescue arg_expr
         or_asgn back_ref nth_ref
         match_with_lvasgn match_current_line
-        module class sclass def defs undef alias args
+        module class sclass def defs def_e defs_e undef alias args
         cbase arg optarg restarg blockarg block_pass kwarg kwoptarg
         kwrestarg kwnilarg send csend super zsuper yield block
         and not or if when case while until while_post
diff --git a/lib/parser/ruby28.y b/lib/parser/ruby28.y
index d95ec3a09..46f509f3e 100644
--- a/lib/parser/ruby28.y
+++ b/lib/parser/ruby28.y
@@ -1232,10 +1232,10 @@ rule
                       @context.push(:def)
                       @current_arg_stack.push(nil)
                     }
-                    f_arglist bodystmt kEND
+                    f_args_body
                     {
                       result = @builder.def_method(val[0], val[1],
-                                  val[3], val[4], val[5])
+                                  *val[3])
 
                       @lexer.cmdarg.pop
                       @lexer.cond.pop
@@ -1255,10 +1255,10 @@ rule
                       @context.push(:defs)
                       @current_arg_stack.push(nil)
                     }
-                    f_arglist bodystmt kEND
+                    f_args_body
                     {
                       result = @builder.def_singleton(val[0], val[1], val[2],
-                                  val[4], val[6], val[7], val[8])
+                                  val[4], *val[6])
 
                       @lexer.cmdarg.pop
                       @lexer.cond.pop
@@ -2515,6 +2515,24 @@ keyword_variable: kNIL
                       result = nil
                     }
 
+     f_args_body: f_arglist bodystmt kEND
+                    {
+                      result = [ val[0], val[1], val[2] ]
+                    }
+                | opt_f_arglist tEQL arg
+                    {
+                      result = [ val[0], val[2], nil ]
+                    }
+
+  opt_f_arglist: f_arglist
+                    {
+                      result = [ val[0] ]
+                    }
+                | # nothing
+                    {
+                      result = [@builder.args(nil, [], nil)]
+                    }
+
        f_arglist: tLPAREN2 f_args rparen
                     {
                       result = @builder.args(val[0], val[1], val[2])
diff --git a/test/test_lexer.rb b/test/test_lexer.rb
index f51373718..05f0cdc09 100644
--- a/test/test_lexer.rb
+++ b/test/test_lexer.rb
@@ -3569,6 +3569,16 @@ def test_ambiguous_integer_re
                    :tIDENTIFIER, 're', [1, 3])
   end
 
+  def test_endless_method
+    setup_lexer(28)
+
+    assert_scanned('def foo = 42',
+                    :kDEF, "def", [0, 3],
+                    :tIDENTIFIER, 'foo', [4, 7],
+                    :tEQL, "=", [8, 9],
+                    :tINTEGER, 42, [10, 12])
+  end
+
   def lex_numbered_parameter(input)
     @lex.max_numparam_stack.push
 
diff --git a/test/test_parser.rb b/test/test_parser.rb
index 5fc1e5111..cc12f1864 100644
--- a/test/test_parser.rb
+++ b/test/test_parser.rb
@@ -9428,4 +9428,54 @@ def test_parser_bug_645
       %{},
       SINCE_1_9)
   end
+
+  def test_endless_method
+    assert_parses(
+      s(:def_e, :foo,
+        s(:args),
+        s(:int, 42)),
+      %q{def foo = 42},
+      %q{~~~ keyword
+        |    ~~~ name
+        |~~~~~~~~~~~~ expression},
+      SINCE_2_8)
+
+    assert_parses(
+      s(:def_e, :inc,
+        s(:args, s(:arg, :x)),
+        s(:send,
+          s(:lvar, :x), :+,
+          s(:int, 1))),
+      %q{def inc(x) = x + 1},
+      %q{~~~ keyword
+        |    ~~~ name
+        |       ~~~ args
+        |~~~~~~~~~~~~~~~~~~ expression},
+      SINCE_2_8)
+
+    assert_parses(
+      s(:defs_e, s(:send, nil, :obj), :foo,
+        s(:args),
+        s(:int, 42)),
+      %q{def obj.foo = 42},
+      %q{~~~ keyword
+        |       ^ operator
+        |        ~~~ name
+        |~~~~~~~~~~~~~~~~ expression},
+      SINCE_2_8)
+
+    assert_parses(
+      s(:defs_e, s(:send, nil, :obj), :inc,
+        s(:args, s(:arg, :x)),
+        s(:send,
+          s(:lvar, :x), :+,
+          s(:int, 1))),
+      %q{def obj.inc(x) = x + 1},
+      %q{~~~ keyword
+        |        ~~~ name
+        |       ^ operator
+        |           ~~~ args
+        |~~~~~~~~~~~~~~~~~~~~~~ expression},
+      SINCE_2_8)
+  end
 end