diff --git a/src/kemal.cr b/src/kemal.cr
index 19d19e9..c25f13e 100644
--- a/src/kemal.cr
+++ b/src/kemal.cr
@@ -8,7 +8,7 @@ require "./kemal/helpers/*"
 
 module Kemal
   # Overload of self.run with the default startup logging
-  def self.run(port = nil)
+  def self.run(port : Int32? = nil)
     self.run port do
       log "[#{config.env}] Kemal is ready to lead at #{config.scheme}://#{config.host_binding}:#{config.port}"
     end
@@ -22,7 +22,7 @@ module Kemal
   # The command to run a `Kemal` application.
   # The port can be given to `#run` but is optional.
   # If not given Kemal will use `Kemal::Config#port`
-  def self.run(port = nil, &block)
+  def self.run(port : Int32? = nil, &block)
     Kemal::CLI.new
     config = Kemal.config
     config.setup
diff --git a/src/kemal/base_log_handler.cr b/src/kemal/base_log_handler.cr
index 33251d6..2b1b992 100644
--- a/src/kemal/base_log_handler.cr
+++ b/src/kemal/base_log_handler.cr
@@ -4,6 +4,6 @@ module Kemal
     include HTTP::Handler
 
     abstract def call(context)
-    abstract def write(message)
+    abstract def write(message : String)
   end
 end
diff --git a/src/kemal/common_exception_handler.cr b/src/kemal/common_exception_handler.cr
index 2b9e3b2..156e27d 100644
--- a/src/kemal/common_exception_handler.cr
+++ b/src/kemal/common_exception_handler.cr
@@ -19,7 +19,7 @@ module Kemal
       end
     end
 
-    private def call_exception_with_status_code(context, exception, status_code)
+    private def call_exception_with_status_code(context : HTTP::Server::Context, exception : Exception, status_code : Int32)
       if Kemal.config.error_handlers.has_key?(status_code)
         context.response.content_type = "text/html" unless context.response.headers.has_key?("Content-Type")
         context.response.print Kemal.config.error_handlers[status_code].call(context, exception)
diff --git a/src/kemal/common_log_handler.cr b/src/kemal/common_log_handler.cr
index e38621d..44eb30f 100644
--- a/src/kemal/common_log_handler.cr
+++ b/src/kemal/common_log_handler.cr
@@ -15,7 +15,7 @@ module Kemal
       context
     end
 
-    def write(message)
+    def write(message : String)
       @handler << message
     end
 
diff --git a/src/kemal/config.cr b/src/kemal/config.cr
index d67ef44..31be2b9 100644
--- a/src/kemal/config.cr
+++ b/src/kemal/config.cr
@@ -93,7 +93,7 @@ module Kemal
       ERROR_HANDLERS
     end
 
-    def add_error_handler(status_code, &handler : HTTP::Server::Context, Exception -> _)
+    def add_error_handler(status_code : Int32, &handler : HTTP::Server::Context, Exception -> _)
       ERROR_HANDLERS[status_code] = ->(context : HTTP::Server::Context, error : Exception) { handler.call(context, error).to_s }
     end
 
diff --git a/src/kemal/dsl.cr b/src/kemal/dsl.cr
index e622a37..6dc9a53 100644
--- a/src/kemal/dsl.cr
+++ b/src/kemal/dsl.cr
@@ -8,18 +8,18 @@ HTTP_METHODS   = %w(get post put patch delete options)
 FILTER_METHODS = %w(get post put patch delete options all)
 
 {% for method in HTTP_METHODS %}
-  def {{method.id}}(path, &block : HTTP::Server::Context -> _)
+  def {{method.id}}(path : String, &block : HTTP::Server::Context -> _)
     raise Kemal::Exceptions::InvalidPathStartException.new({{method}}, path) unless Kemal::Utils.path_starts_with_slash?(path)
     Kemal::RouteHandler::INSTANCE.add_http_route({{method}}.upcase, path, &block)
   end
 {% end %}
 
-def ws(path, &block : HTTP::WebSocket, HTTP::Server::Context -> Void)
+def ws(path : String, &block : HTTP::WebSocket, HTTP::Server::Context -> Void)
   raise Kemal::Exceptions::InvalidPathStartException.new("ws", path) unless Kemal::Utils.path_starts_with_slash?(path)
   Kemal::WebSocketHandler.new path, &block
 end
 
-def error(status_code, &block : HTTP::Server::Context, Exception -> _)
+def error(status_code : Int32, &block : HTTP::Server::Context, Exception -> _)
   Kemal.config.add_error_handler status_code, &block
 end
 
@@ -28,7 +28,7 @@ end
 #  - after_all, after_get, after_post, after_put, after_patch, after_delete, after_options
 {% for type in ["before", "after"] %}
   {% for method in FILTER_METHODS %}
-    def {{type.id}}_{{method.id}}(path = "*", &block : HTTP::Server::Context -> _)
+    def {{type.id}}_{{method.id}}(path : String = "*", &block : HTTP::Server::Context -> _)
      Kemal::FilterHandler::INSTANCE.{{type.id}}({{method}}.upcase, path, &block)
     end
   {% end %}
diff --git a/src/kemal/ext/context.cr b/src/kemal/ext/context.cr
index ba8a834..6b99095 100644
--- a/src/kemal/ext/context.cr
+++ b/src/kemal/ext/context.cr
@@ -15,10 +15,10 @@ class HTTP::Server
     def params
       connection_type = @request.headers.fetch("Connection", nil)
       @request.url_params ||= unless connection_type == "Upgrade"
-                                route_lookup.params
-                              else
-                                ws_route_lookup.params
-                              end
+        route_lookup.params
+      else
+        ws_route_lookup.params
+      end
 
       @params ||= if @request.param_parser
                     @request.param_parser.not_nil!
@@ -27,7 +27,7 @@ class HTTP::Server
                   end
     end
 
-    def redirect(url, status_code = 302)
+    def redirect(url : String, status_code : Int32 = 302)
       @response.headers.add "Location", url
       @response.status_code = status_code
     end
@@ -48,11 +48,11 @@ class HTTP::Server
       ws_route_lookup.found?
     end
 
-    def get(name)
+    def get(name : String)
       @store[name]
     end
 
-    def set(name, value)
+    def set(name : String, value : StoreTypes)
       @store[name] = value
     end
   end
diff --git a/src/kemal/ext/request.cr b/src/kemal/ext/request.cr
index f027de5..1f3fc6a 100644
--- a/src/kemal/ext/request.cr
+++ b/src/kemal/ext/request.cr
@@ -8,7 +8,7 @@ class HTTP::Request
   end
 
   # Checks if method contained in _method param is valid one
-  def self.override_method_valid?(override_method)
+  def self.override_method_valid?(override_method : String)
     return false unless override_method.is_a?(String)
     override_method = override_method.upcase
     override_method == "PUT" || override_method == "PATCH" || override_method == "DELETE"
diff --git a/src/kemal/handler.cr b/src/kemal/handler.cr
index e06ae27..b9f8637 100644
--- a/src/kemal/handler.cr
+++ b/src/kemal/handler.cr
@@ -63,7 +63,7 @@ module Kemal
       @@exclude_routes_tree.find(radix_path(env.request.method, env.request.path)).found?
     end
 
-    private def radix_path(method : String, path)
+    private def radix_path(method : String, path : String)
       "#{self.class}/#{method.downcase}#{path}"
     end
   end
diff --git a/src/kemal/helpers/helpers.cr b/src/kemal/helpers/helpers.cr
index 3edb826..63da82a 100644
--- a/src/kemal/helpers/helpers.cr
+++ b/src/kemal/helpers/helpers.cr
@@ -8,23 +8,23 @@
 # - Kemal::StaticFileHandler
 # - Here goes custom handlers
 # - Kemal::RouteHandler
-def add_handler(handler)
+def add_handler(handler : HTTP::Handler)
   Kemal.config.add_handler handler
 end
 
-def add_handler(handler, position : Int32)
+def add_handler(handler : HTTP::Handler, position : Int32)
   Kemal.config.add_handler handler, position
 end
 
 # Sets public folder from which the static assets will be served.
 # By default this is `/public` not `src/public`.
-def public_folder(path)
+def public_folder(path : String)
   Kemal.config.public_folder = path
 end
 
 # Logs the output via `logger`.
 # This is the built-in `Kemal::CommonLogHandler` by default which uses STDOUT.
-def log(message)
+def log(message : String)
   Kemal.config.logger.write "#{message}\n"
 end
 
@@ -32,7 +32,7 @@ end
 # This is enabled by default.
 #
 #   logging false
-def logging(status)
+def logging(status : Bool)
   Kemal.config.logging = status
 end
 
@@ -57,7 +57,7 @@ end
 # Now that we have a custom logger here's how we use it
 #
 #   logger MyCustomLogger.new
-def logger(logger)
+def logger(logger : Kemal::BaseLogHandler)
   Kemal.config.logger = logger
   Kemal.config.add_handler logger
 end
@@ -81,7 +81,7 @@ end
 #   def call(env)
 #     headers(env, {"custom-header" => "This is a custom value"})
 #   end
-def headers(env, additional_headers)
+def headers(env : HTTP::Server::Context, additional_headers : Hash(String, String))
   env.response.headers.merge!(additional_headers)
 end
 
diff --git a/src/kemal/helpers/utils.cr b/src/kemal/helpers/utils.cr
index 6dcab66..9764dec 100644
--- a/src/kemal/helpers/utils.cr
+++ b/src/kemal/helpers/utils.cr
@@ -1,14 +1,14 @@
 module Kemal
   module Utils
-    def self.path_starts_with_slash?(path)
+    def self.path_starts_with_slash?(path : String)
       path.starts_with?("/")
     end
 
-    def self.zip_types(path) # https://github.com/h5bp/server-configs-nginx/blob/master/nginx.conf
+    def self.zip_types(path : String) # https://github.com/h5bp/server-configs-nginx/blob/master/nginx.conf
       [".htm", ".html", ".txt", ".css", ".js", ".svg", ".json", ".xml", ".otf", ".ttf", ".woff", ".woff2"].includes? File.extname(path)
     end
 
-    def self.mime_type(path)
+    def self.mime_type(path : String)
       case File.extname(path)
       when ".txt"          then "text/plain"
       when ".htm", ".html" then "text/html"
diff --git a/src/kemal/null_log_handler.cr b/src/kemal/null_log_handler.cr
index e636465..9f3e03a 100644
--- a/src/kemal/null_log_handler.cr
+++ b/src/kemal/null_log_handler.cr
@@ -1,11 +1,11 @@
 module Kemal
   # This is here to represent the logger corresponding to Null Object Pattern.
   class NullLogHandler < Kemal::BaseLogHandler
-    def call(context)
+    def call(context : HTTP::Server::Context)
       call_next(context)
     end
 
-    def write(message)
+    def write(message : String)
     end
   end
 end
diff --git a/src/kemal/route.cr b/src/kemal/route.cr
index 1117548..a97451c 100644
--- a/src/kemal/route.cr
+++ b/src/kemal/route.cr
@@ -7,7 +7,7 @@ module Kemal
     @handler : HTTP::Server::Context -> String
     @method : String
 
-    def initialize(@method, @path : String, &handler : HTTP::Server::Context -> _)
+    def initialize(@method : String, @path : String, &handler : HTTP::Server::Context -> _)
       @handler = ->(context : HTTP::Server::Context) do
         handler.call(context).to_s
       end
diff --git a/src/kemal/ssl.cr b/src/kemal/ssl.cr
index eac0599..e205b18 100644
--- a/src/kemal/ssl.cr
+++ b/src/kemal/ssl.cr
@@ -6,11 +6,11 @@ module Kemal
       @context = OpenSSL::SSL::Context::Server.new
     end
 
-    def key_file=(key_file)
+    def key_file=(key_file : String)
       @context.private_key = key_file
     end
 
-    def cert_file=(cert_file)
+    def cert_file=(cert_file : String)
       @context.certificate_chain = cert_file
     end
   end