diff --git a/dedocutils/preprocessing/skew_corrector.py b/dedocutils/preprocessing/skew_corrector.py
index 9c293ea..69d4ffb 100644
--- a/dedocutils/preprocessing/skew_corrector.py
+++ b/dedocutils/preprocessing/skew_corrector.py
@@ -40,7 +40,7 @@ def preprocess(self, image: np.ndarray, parameters: Optional[dict] = None) -> Tu
             best_angle = angles[scores.index(max(scores))]
 
         rotated = rotate_image(image, best_angle)
-        return rotated, {"rotated_angle": orientation_angle + best_angle}
+        return rotated, {"rotated_angle": float(orientation_angle + best_angle)}
 
     def __determine_score(self, arr: np.ndarray, angle: int) -> Tuple[np.ndarray, float]:
         data = rotate_image(arr, angle)