diff --git a/spec/middleware/csrf_spec.cr b/spec/middleware/csrf_spec.cr
index c454811..62aae20 100644
--- a/spec/middleware/csrf_spec.cr
+++ b/spec/middleware/csrf_spec.cr
@@ -47,7 +47,7 @@ describe "Kemal::Middleware::CSRF" do
     client_response = HTTP::Client::Response.from_io(io, decompress: false)
     client_response.status_code.should eq 403
 
-    current_token = context.session["csrf"]
+    current_token = context.session["csrf"].as(String)
 
     handler = Kemal::Middleware::CSRF.new
     request = HTTP::Request.new("POST", "/",
diff --git a/src/kemal/session.cr b/src/kemal/session.cr
index f971d5e..011dfe3 100644
--- a/src/kemal/session.cr
+++ b/src/kemal/session.cr
@@ -17,6 +17,9 @@ module Kemal
   class Sessions
     NAME = "SessionId"
 
+    # Session Types are String, Integer, Float and Boolean
+    alias SessionTypes = String | Int64 | Float64 | Bool
+
     # I hate websites which require daily login so the default
     # inactivity timeout is 48 hours.
     TTL = 48.hours
@@ -38,7 +41,7 @@ module Kemal
 
       def initialize(@id)
         @last_access_at = Time.new.epoch_ms
-        @store = Hash(String, String).new
+        @store = Hash(String, SessionTypes).new
       end
 
       def [](key : String)
@@ -51,7 +54,7 @@ module Kemal
         @store[key]?
       end
 
-      def []=(key : String, value : String)
+      def []=(key : String, value : SessionTypes)
         @last_access_at = Time.now.epoch_ms
         @store[key] = value
       end
@@ -77,7 +80,7 @@ module Kemal
       @id = id
     end
 
-    def []=(key : String, value : String)
+    def []=(key : String, value : SessionTypes)
       store = STORE[id]? || begin
         STORE[id] = Session.new(id)
       end