diff --git a/Upsilon/Binder/Binder.cs b/Upsilon/Binder/Binder.cs
index 4a31e11..d5cffc0 100644
--- a/Upsilon/Binder/Binder.cs
+++ b/Upsilon/Binder/Binder.cs
@@ -194,7 +194,6 @@ namespace Upsilon.Binder
             var expression = BindExpression(e.Identifier);
             if (expression.Type != Type.Function && expression.Type != Type.Unknown)
             {
-                //TODO Better error
                 _diagnostics.LogError($"Unknown function called.", e.Span);
                 return new BoundLiteralExpression(new ScriptNull(), e.Span);
             }
@@ -232,9 +231,33 @@ namespace Upsilon.Binder
 
                 returnType = function.ResultType;
 
+                var pars = function.Parameters;
+                if (pars.Length != parameters.Count)
+                {
+                    _diagnostics.LogError(
+                        $"Invalid number of parameters for function '{function.Name}'. Expected {pars.Length}, got {parameters.Count}",
+                        e.Span);
+                }
+                else
+                {
+                    for (var i = 0; i < pars.Length; i++)
+                    {
+                        var functionParameter = pars[i];
+                        var callingParameter = parameters[i];
+                        if (functionParameter.Type != Type.Unknown &&
+                            callingParameter.Type != Type.Unknown && callingParameter.Type != Type.Nil)
+                        {
+                            if (callingParameter.Type != functionParameter.Type)
+                            {
+                                _diagnostics.LogError(
+                                    $"Invalid type for function '{function.Name}' at parameter '{functionParameter.Name}'. " +
+                                    $"Expected type '{functionParameter.Type}', got '{callingParameter.Type}'",
+                                    callingParameter.Span);
+                            }
+                        }
+                    }
+                }
             }
-
-            //TODO: validate parameters
             return new BoundFunctionCallExpression(expression, parameters.ToImmutable(), e.Span, returnType);
         }
 
@@ -470,7 +493,7 @@ namespace Upsilon.Binder
 
             foreach (var parameter in func.Parameters)
             {
-                var vari = new VariableSymbol(parameter.VariableSymbol.Name, Type.Unknown, true);
+                var vari = new VariableSymbol(parameter.VariableSymbol.Name, parameter.VariableSymbol.Type, true);
                 parameters.Add(vari);
                 innerScope.DefineLocalVariable(vari);
             }
@@ -499,7 +522,7 @@ namespace Upsilon.Binder
                 // don't allow assigning different typed variables to a variable, unless either of them is nil, allow assigning nil to all variables
                 if (variable.Type != Type.Function)
                 {
-                    if (variable.Type == Type.Nil )
+                    if (variable.Type == Type.Nil || variable.Type == Type.Unknown)
                     {
                         variable.Type = Type.Function;
                     }