diff --git a/CubicNoise/EngineParameters.cs b/CubicNoise/EngineParameters.cs
index 135be2e..1ebaf04 100644
--- a/CubicNoise/EngineParameters.cs
+++ b/CubicNoise/EngineParameters.cs
@@ -11,6 +11,6 @@ namespace CubicNoise
 
         public NoiseTypes Type { get; set; } = NoiseTypes.UNKNOWN;
 
-        public Dictionary<IParameterName, int> IntParameters { get; set; }
+        public IReadOnlyDictionary<IParameterName, int> IntParameters { get; set; }
     }
 }
diff --git a/CubicNoise/NoiseEngine.cs b/CubicNoise/NoiseEngine.cs
index 1688915..9e448f7 100644
--- a/CubicNoise/NoiseEngine.cs
+++ b/CubicNoise/NoiseEngine.cs
@@ -10,7 +10,7 @@ namespace CubicNoise
     {
         private readonly INoiseEngine engine;
 
-        private NoiseEngine(NoiseTypes type, int seed, Dictionary<IParameterName, int> intParameters)
+        private NoiseEngine(NoiseTypes type, int seed, IReadOnlyDictionary<IParameterName, int> intParameters)
         {
             this.engine = type switch
             {