diff --git a/linear_regression.py b/linear_regression.py
index 2e8d223..3d99082 100644
--- a/linear_regression.py
+++ b/linear_regression.py
@@ -21,6 +21,9 @@ class Regression:
 
     def predict(self, *, x: int | float = None, y: int | float = None) -> float:
         """predict a value if x or y is given"""
+        if x is not None and y is not None:
+            msg = "predict() expects one keyword argument 'x' or 'y', got both"
+            raise TypeError(msg)
         if x is not None:
             return self.intercept + x * self.coefficient
         if y is not None:
@@ -77,6 +80,9 @@ def test_regression_predict_exceptions(example_data):
     with pytest.raises(TypeError, match="expects a keyword"):
         regression.predict()
 
+    with pytest.raises(TypeError, match="expects one keyword"):
+        regression.predict(x=1, y=2)
+
     with pytest.raises(TypeError, match="takes 1 positional argument but"):
         regression.predict(1)