diff --git a/pyerrors/linalg.py b/pyerrors/linalg.py
index 507569b2..61740e40 100644
--- a/pyerrors/linalg.py
+++ b/pyerrors/linalg.py
@@ -213,8 +213,6 @@ def _scalar_mat_op(op, obs, **kwargs):
     """Computes the matrix to scalar operation op to a given matrix of Obs."""
     def _mat(x, **kwargs):
         dim = int(np.sqrt(len(x)))
-        if np.sqrt(len(x)) != dim:
-            raise Exception('Input has to have dim**2 entries')
 
         mat = []
         for i in range(dim):
@@ -227,8 +225,6 @@ def _scalar_mat_op(op, obs, **kwargs):
 
     if isinstance(obs, np.ndarray):
         raveled_obs = (1 * (obs.ravel())).tolist()
-    elif isinstance(obs, list):
-        raveled_obs = obs
     else:
         raise TypeError('Unproper type of input.')
     return derived_observable(_mat, raveled_obs, **kwargs)
diff --git a/tests/linalg_test.py b/tests/linalg_test.py
index f446d972..61c71514 100644
--- a/tests/linalg_test.py
+++ b/tests/linalg_test.py
@@ -314,6 +314,8 @@ def test_matrix_functions():
     # Check determinant
     assert pe.linalg.det(np.diag(np.diag(matrix))) == np.prod(np.diag(matrix))
 
+    pe.linalg.pinv(matrix[:,:3])
+
 
 def test_complex_matrix_operations():
     dimension = 4