diff --git a/Gemfile b/Gemfile
index 58c28f79..870fde0e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -15,6 +15,6 @@ gem "memory_profiler"
 # Recent steep requires Ruby >= 3.0.0.
 # Then skip install on some CI jobs.
 if !ENV['GITHUB_ACTION'] || ENV['INSTALL_STEEP'] == 'true'
-  gem "rbs", "3.6.0", require: false
-  gem "steep", "1.8.0", require: false
+  gem "rbs", "3.7.0", require: false
+  gem "steep", "1.9.1", require: false
 end
diff --git a/lib/lrama/bitmap.rb b/lib/lrama/bitmap.rb
index 23cbd30d..b2de0248 100644
--- a/lib/lrama/bitmap.rb
+++ b/lib/lrama/bitmap.rb
@@ -13,7 +13,7 @@ def self.from_array(ary)
     end
 
     def self.to_array(int)
-      a = []
+      a = [] #: Array[Integer]
       i = 0
 
       while int > 0 do
diff --git a/lib/lrama/grammar.rb b/lib/lrama/grammar.rb
index 3724f828..ee57b3c5 100644
--- a/lib/lrama/grammar.rb
+++ b/lib/lrama/grammar.rb
@@ -382,7 +382,7 @@ def fill_sym_to_rules
     end
 
     def validate_rule_lhs_is_nterm!
-      errors = []
+      errors = [] #: Array[String]
 
       rules.each do |rule|
         next if rule.lhs.nterm?
diff --git a/lib/lrama/grammar/parameterizing_rule/rhs.rb b/lib/lrama/grammar/parameterizing_rule/rhs.rb
index d574841d..f60781c0 100644
--- a/lib/lrama/grammar/parameterizing_rule/rhs.rb
+++ b/lib/lrama/grammar/parameterizing_rule/rhs.rb
@@ -16,7 +16,7 @@ def resolve_user_code(bindings)
           return unless user_code
 
           resolved = Lexer::Token::UserCode.new(s_value: user_code.s_value, location: user_code.location)
-          var_to_arg = {}
+          var_to_arg = {} #: Hash[String, String]
           symbols.each do |sym|
             resolved_sym = bindings.resolve_symbol(sym)
             if resolved_sym != sym
diff --git a/lib/lrama/grammar/rule_builder.rb b/lib/lrama/grammar/rule_builder.rb
index f6df22b6..06097eb7 100644
--- a/lib/lrama/grammar/rule_builder.rb
+++ b/lib/lrama/grammar/rule_builder.rb
@@ -67,7 +67,7 @@ def has_inline_rules?
       end
 
       def resolve_inline_rules
-        resolved_builders = []
+        resolved_builders = [] #: Array[RuleBuilder]
         rhs.each_with_index do |token, i|
           if (inline_rule = @parameterizing_rule_resolver.find_inline(token))
             inline_rule.rhs_list.each do |inline_rhs|
diff --git a/lib/lrama/lexer/token/user_code.rb b/lib/lrama/lexer/token/user_code.rb
index 97122086..c606200d 100644
--- a/lib/lrama/lexer/token/user_code.rb
+++ b/lib/lrama/lexer/token/user_code.rb
@@ -16,7 +16,7 @@ def references
 
         def _references
           scanner = StringScanner.new(s_value)
-          references = []
+          references = [] #: Array[Grammar::Reference]
 
           until scanner.eos? do
             case
diff --git a/lib/lrama/state/reduce.rb b/lib/lrama/state/reduce.rb
index a2b7c26c..54ab87b4 100644
--- a/lib/lrama/state/reduce.rb
+++ b/lib/lrama/state/reduce.rb
@@ -26,9 +26,8 @@ def add_not_selected_symbol(sym)
       end
 
       def selected_look_ahead
-        if @look_ahead
-          # @type ivar @look_ahead: Array<Grammar::Symbol>
-          @look_ahead - @not_selected_symbols
+        if look_ahead
+          look_ahead - @not_selected_symbols
         else
           []
         end
diff --git a/rbs_collection.lock.yaml b/rbs_collection.lock.yaml
index b53cb101..2e642e97 100644
--- a/rbs_collection.lock.yaml
+++ b/rbs_collection.lock.yaml
@@ -1,6 +1,14 @@
 ---
 path: ".gem_rbs_collection"
 gems:
+- name: diff-lcs
+  version: '1.5'
+  source:
+    type: git
+    name: ruby/gem_rbs_collection
+    revision: f2fa96be08e0f7fe5237a45d2b69d9d7a5d0b416
+    remote: https://github.com/ruby/gem_rbs_collection.git
+    repo_dir: gems
 - name: erb
   version: '0'
   source:
@@ -18,7 +26,7 @@ gems:
   source:
     type: git
     name: ruby/gem_rbs_collection
-    revision: 4b0d2f72e63b6c3e92dc54e19ce23dd24524f9a7
+    revision: f2fa96be08e0f7fe5237a45d2b69d9d7a5d0b416
     remote: https://github.com/ruby/gem_rbs_collection.git
     repo_dir: gems
 - name: stackprof
@@ -26,7 +34,7 @@ gems:
   source:
     type: git
     name: ruby/gem_rbs_collection
-    revision: 4b0d2f72e63b6c3e92dc54e19ce23dd24524f9a7
+    revision: f2fa96be08e0f7fe5237a45d2b69d9d7a5d0b416
     remote: https://github.com/ruby/gem_rbs_collection.git
     repo_dir: gems
 - name: strscan