diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_basis.py b/tests/test_basis.py
index 3478c9a..2d45740 100644
--- a/tests/test_basis.py
+++ b/tests/test_basis.py
@@ -8,7 +8,7 @@
 	LaguerreTensorBasis, 
 	HermiteTensorBasis)
 
-from checkder import check_jacobian, check_hessian 
+from .checkder import check_jacobian, check_hessian 
 
 
 def test_equivalence(m = 3, p = 5):
diff --git a/tests/test_demos.py b/tests/test_demos.py
index 994da2b..c6e3f0c 100644
--- a/tests/test_demos.py
+++ b/tests/test_demos.py
@@ -1,6 +1,6 @@
 from __future__ import print_function
 from psdr.demos import GolinskiGearbox, Borehole, OTLCircuit, Piston, RobotArm, WingWeight
-from checkder import check_derivative
+from .checkder import check_derivative
 
 def test_grad():
 	
diff --git a/tests/test_gp.py b/tests/test_gp.py
index 20a07c0..170f88d 100644
--- a/tests/test_gp.py
+++ b/tests/test_gp.py
@@ -1,7 +1,7 @@
 from __future__ import print_function
 import numpy as np
 from psdr import GaussianProcess, BoxDomain, Function 
-from checkder import check_gradient 
+from .checkder import check_gradient 
 
 def test_gp_der(m = 5, M = 50):
 	np.random.seed(0)
diff --git a/tests/test_poly.py b/tests/test_poly.py
index 8e42a6b..37d37f8 100644
--- a/tests/test_poly.py
+++ b/tests/test_poly.py
@@ -2,7 +2,7 @@
 import numpy as np
 
 from psdr import PolynomialApproximation, PolynomialFunction, LegendreTensorBasis, BoxDomain
-from checkder import *
+from .checkder import *
 
 def test_poly_der(dimension = 3, degree = 5):
 	coef = np.random.randn(len(LegendreTensorBasis(dimension, degree)))
diff --git a/tests/test_polyridge.py b/tests/test_polyridge.py
index bb4d191..95d27e3 100644
--- a/tests/test_polyridge.py
+++ b/tests/test_polyridge.py
@@ -2,7 +2,7 @@
 import numpy as np
 import scipy.linalg
 from psdr import PolynomialRidgeApproximation, LegendreTensorBasis, PolynomialRidgeFunction
-from checkder import *
+from .checkder import *
 
 
 def test_affine():