diff --git a/xFunc.Maths/Expressions/Matrices/VectorValue.cs b/xFunc.Maths/Expressions/Matrices/VectorValue.cs
index 752fc247f..806589709 100644
--- a/xFunc.Maths/Expressions/Matrices/VectorValue.cs
+++ b/xFunc.Maths/Expressions/Matrices/VectorValue.cs
@@ -174,12 +174,12 @@ public NumberValue Average()
     /// <returns>The sum of the values in the vector.</returns>
     public NumberValue Sum()
     {
-        var sum = NumberValue.Zero;
+        var sum = 0.0;
 
-        for (var i = 0; i < Size; i++)
-            sum += array[i];
+        for (var i = 0; i < array.Length; i++)
+            sum += array[i].Number;
 
-        return sum;
+        return new NumberValue(sum);
     }
 
     /// <summary>
diff --git a/xFunc.Maths/Tokenization/Lexer.KeywordToken.cs b/xFunc.Maths/Tokenization/Lexer.KeywordToken.cs
index df2ec7f68..c4f329d1a 100644
--- a/xFunc.Maths/Tokenization/Lexer.KeywordToken.cs
+++ b/xFunc.Maths/Tokenization/Lexer.KeywordToken.cs
@@ -21,9 +21,11 @@ private bool CreateKeywordToken()
 
         var keyword = function[..endIndex];
 
-        var lowerKeyword = keyword.Length <= 1024
-            ? stackalloc char[keyword.Length]
-            : new char[keyword.Length];
+        // keyword shouldn't be bigger than the biggest valid keyword
+        if (keyword.Length > "unassign".Length)
+            return false;
+
+        Span<char> lowerKeyword = stackalloc char[keyword.Length];
 
         keyword.ToLowerInvariant(lowerKeyword);
 
diff --git a/xFunc.Maths/Tokenization/Lexer.StringToken.cs b/xFunc.Maths/Tokenization/Lexer.StringToken.cs
index 7a63dada9..71ad10e6f 100644
--- a/xFunc.Maths/Tokenization/Lexer.StringToken.cs
+++ b/xFunc.Maths/Tokenization/Lexer.StringToken.cs
@@ -13,20 +13,8 @@ private bool CreateStringToken(char quote)
         if (function[0] != quote)
             return false;
 
-        var endIndex = 1;
-        var foundClosingQuote = false;
-        while (endIndex < function.Length)
-        {
-            if (function[endIndex] == quote)
-            {
-                foundClosingQuote = true;
-                break;
-            }
-
-            endIndex++;
-        }
-
-        if (!foundClosingQuote)
+        var endIndex = function[1..].IndexOf(quote) + 1;
+        if (endIndex == 0)
             throw new TokenizeException(Resource.StringTokenizeException);
 
         var stringValue = function[1..endIndex];