diff --git a/ConfigGenerator.Tests/TestFiles/appsettings.json b/ConfigGenerator.Tests/TestFiles/appsettings.json
index a241754..879cb23 100644
--- a/ConfigGenerator.Tests/TestFiles/appsettings.json
+++ b/ConfigGenerator.Tests/TestFiles/appsettings.json
@@ -10,8 +10,12 @@
   "DuplicateEntryOnlyShowsOnce": false,
   "IntValue": 1,
   "DoubleValue": 2.2,
+  "LongValue": 9223372036854775807,
+  "ULongValue": 18446744073709551615,
   "ArrayWithDoubles": [1.1, 2.245, 4.67],
   "ArrayWithStrings": [ "Key1", "Value 1" ],
   "ArrayWithInts": [ 1, 2 ],
-  "ArrayWithBools": [ true, false, true ]  
+  "ArrayWithBools": [ true, false, true ],
+  "ArrayWithLongs": [ 9223372036854775807, 1234567890123456789 ],
+  "ArrayWithULongs": [ 18446744073709551615, 1234567890123456789 ]
 }
diff --git a/ConfigGenerator.Tests/TestFiles/expected.cs b/ConfigGenerator.Tests/TestFiles/expected.cs
index 4c5b641..2bb2ccc 100644
--- a/ConfigGenerator.Tests/TestFiles/expected.cs
+++ b/ConfigGenerator.Tests/TestFiles/expected.cs
@@ -1,5 +1,4 @@
-
-using System;
+using System;
 using System.Collections.Generic;
 
 namespace ApplicationConfig
@@ -11,10 +10,14 @@ public class MyAppConfig
         public bool DuplicateEntryOnlyShowsOnce { get; set; }
         public int IntValue { get; set; }
         public double DoubleValue { get; set; }
+        public long LongValue { get; set; }
+        public ulong ULongValue { get; set; }
         public IEnumerable<double> ArrayWithDoubles { get; set; }
         public IEnumerable<string> ArrayWithStrings { get; set; }
         public IEnumerable<int> ArrayWithInts { get; set; }
         public IEnumerable<bool> ArrayWithBools { get; set; }
+        public IEnumerable<long> ArrayWithLongs { get; set; }
+        public IEnumerable<ulong> ArrayWithULongs { get; set; }
         public bool ShowDeveloperWarnings { get; set; }
         public Logging Logging { get; set; }
     }
diff --git a/src/GenerateConfigClasses.cs b/src/GenerateConfigClasses.cs
index dd63806..2f2574f 100644
--- a/src/GenerateConfigClasses.cs
+++ b/src/GenerateConfigClasses.cs
@@ -135,11 +135,20 @@ private static string GetPropertyTypeNameBasedOnValue(JsonElement value)
         {
             return value.ValueKind switch
             {
-                JsonValueKind.Number => value.TryGetInt32(out _) ? "int" : "double",
+                JsonValueKind.Number => DetermineNumericType(value),
                 JsonValueKind.True or JsonValueKind.False => "bool",
                 _ => "string",
             };
         }
+        
+        private static string DetermineNumericType(JsonElement value)
+        {
+            if (value.TryGetInt32(out _)) return "int";
+            if (value.TryGetInt64(out _)) return "long";
+            if (value.TryGetUInt64(out _)) return "ulong";
+
+            return "double"; 
+        }
 
         private static string NormalizePropertyName(string originalName)
         {
@@ -218,4 +227,4 @@ private static void MergeDictionaries(Dictionary<string, object> dictionary1, Di
             }
         }
     }
-}
+}
\ No newline at end of file