diff --git a/lib/prism/node_ext.rb b/lib/prism/node_ext.rb
index aa9dba57c7d89e..8a6624e76dad77 100644
--- a/lib/prism/node_ext.rb
+++ b/lib/prism/node_ext.rb
@@ -329,10 +329,7 @@ def signature
         case param
         when MultiTargetNode
           names << [:req]
-        when NoKeywordsParameterNode, KeywordRestParameterNode,
-            NoBlockParameterNode, BlockParameterNode,
-            ForwardingParameterNode
-          # Invalid syntax, e.g. "def f(**nil, ...)" moves the NoKeywordsParameterNode to posts
+        when ErrorRecoveryNode
           raise "Invalid syntax"
         else
           names << [:req, param.name]
diff --git a/prism/config.yml b/prism/config.yml
index 7c283741d3b52c..bbbc5f3d336ae0 100644
--- a/prism/config.yml
+++ b/prism/config.yml
@@ -1017,7 +1017,9 @@ nodes:
                       ^  ^
       - name: rest
         type: node?
-        kind: pattern expression
+        kind:
+          - ImplicitRestNode
+          - SplatNode
         comment: |
           Represents the rest element of the array pattern.
 
diff --git a/string.c b/string.c
index 19b8a1e225c32a..ef0e3864ea31dd 100644
--- a/string.c
+++ b/string.c
@@ -4920,9 +4920,9 @@ rb_str_byterindex(VALUE str, VALUE sub, long pos)
  *    s.size              # => 3 # Three 1-byte characters.
  *    s.bytesize          # => 3 # Three bytes.
  *    s.byterindex('f')   # => 0
-      s.byterindex('o')   # => 2
-      s.byterindex('oo')  # => 1
-      s.byterindex('ooo') # => nil
+ *    s.byterindex('o')   # => 2
+ *    s.byterindex('oo')  # => 1
+ *    s.byterindex('ooo') # => nil
  *
  *  When +object+ is a Regexp,
  *  returns the index of the last found substring matching +object+;
diff --git a/test/prism/ruby/parameters_signature_test.rb b/test/prism/ruby/parameters_signature_test.rb
index 5a225862c338bb..1ca2b144a91b8d 100644
--- a/test/prism/ruby/parameters_signature_test.rb
+++ b/test/prism/ruby/parameters_signature_test.rb
@@ -77,6 +77,13 @@ def test_forwarding
       assert_parameters([[:rest, :*], [:keyrest, :**], [:block, :&]], "...")
     end
 
+    def test_invalid_syntax
+      e = assert_raise(RuntimeError) do
+        Prism.parse_statement("def f(**nil, ...); end").parameters.signature
+      end
+      assert_equal("Invalid syntax", e.message)
+    end
+
     private
 
     def assert_parameters(expected, source, compare: true)
diff --git a/tool/lib/leakchecker.rb b/tool/lib/leakchecker.rb
index 36662e9a46761d..33a546699f6145 100644
--- a/tool/lib/leakchecker.rb
+++ b/tool/lib/leakchecker.rb
@@ -113,9 +113,15 @@ def check_fd_leak(test_name)
       }
       unless fd_leaked.empty?
         unless @@try_lsof == false
-          open_list = IO.popen(%W[lsof -w -a -d #{fd_leaked.minmax.uniq.join("-")} -p #$$], &:readlines)
-          if @@try_lsof |= $?.success?
-            columns = (header = open_list.shift).split
+          begin
+            open_list = IO.popen(%W[lsof -w -a -d #{fd_leaked.minmax.uniq.join("-")} -p #$$], &:readlines)
+          rescue
+            @@try_lsof = false
+          else
+            @@try_lsof |= $?.success?
+          end
+          if header = open_list&.shift
+            columns = header.split
             fd_index, node_index = columns.index('FD'), columns.index('NODE')
             open_list.reject! do |of|
               of = of.chomp.split(' ', node_index + 2)
@@ -129,8 +135,8 @@ def check_fd_leak(test_name)
                 false
               end
             end
+            puts(header, open_list) unless open_list.empty?
           end
-          puts(header, open_list) unless open_list.empty?
         end
       end
       inspect.each {|fd, (str, pos)|