diff --git a/math/src/main/java/com/github/signaflo/math/linear/doubles/QuadraticForm.java b/math/src/main/java/com/github/signaflo/math/linear/doubles/QuadraticForm.java
index 8465b6e..384ee45 100644
--- a/math/src/main/java/com/github/signaflo/math/linear/doubles/QuadraticForm.java
+++ b/math/src/main/java/com/github/signaflo/math/linear/doubles/QuadraticForm.java
@@ -64,8 +64,8 @@ public static double multiply(Vector x, Matrix A) {
     }
 
     private static void validateArguments(Vector x, Matrix A) {
-        Validate.argumentsNotNull(x.getClass(), x);
-        Validate.argumentsNotNull(A.getClass(), A);
+        Validate.argumentsNotNull(Vector.class, x);
+        Validate.argumentsNotNull(Matrix.class, A);
         if (!A.isSquare()) {
             throw new IllegalArgumentException("The matrix must be square.");
         }