diff --git a/kwave/utils/matlab.py b/kwave/utils/matlab.py
index 2e040157..c23d4e67 100644
--- a/kwave/utils/matlab.py
+++ b/kwave/utils/matlab.py
@@ -47,7 +47,7 @@ def matlab_assign(matrix: np.ndarray, indices: Union[int, np.ndarray],
 
     """
     original_shape = matrix.shape
-    matrix = matrix.flatten(order='F')
+    matrix = np.ravel(matrix, order='F')
     matrix[indices] = values
     return matrix.reshape(original_shape, order='F')