diff --git a/GPy/core/parameterization/array_core.py b/GPy/core/parameterization/observable_array.py
similarity index 100%
rename from GPy/core/parameterization/array_core.py
rename to GPy/core/parameterization/observable_array.py
diff --git a/GPy/core/parameterization/param.py b/GPy/core/parameterization/param.py
index 182af902..60bdfe9d 100644
--- a/GPy/core/parameterization/param.py
+++ b/GPy/core/parameterization/param.py
@@ -4,7 +4,7 @@
 import itertools
 import numpy
 from parameter_core import OptimizationHandlable, adjust_name_for_printing
-from array_core import ObsAr
+from observable_array import ObsAr
 
 ###### printing
 __constraints_name__ = "Constraint"
diff --git a/GPy/likelihoods/__init__.py b/GPy/likelihoods/__init__.py
index cf3f4287..5d5d692a 100644
--- a/GPy/likelihoods/__init__.py
+++ b/GPy/likelihoods/__init__.py
@@ -4,11 +4,19 @@ from gaussian import Gaussian
 from gamma import Gamma
 from poisson import Poisson
 from student_t import StudentT
-from sstudent_t import SstudentT
 from likelihood import Likelihood
 from mixed_noise import MixedNoise
-from symbolic import Symbolic
-from negative_binomial import Negative_binomial
-from skew_normal import Skew_normal
-from skew_exponential import Skew_exponential
-from null_category import Null_category
+# TODO need to fix this in a config file.
+try:
+    import sympy as sym
+    sympy_available=True
+except ImportError:
+    sympy_available=False
+if sympy_available:
+    # These are likelihoods that rely on symbolic.
+    from symbolic import Symbolic
+    from sstudent_t import SstudentT
+    from negative_binomial import Negative_binomial
+    from skew_normal import Skew_normal
+    from skew_exponential import Skew_exponential
+    from null_category import Null_category
diff --git a/GPy/testing/parameterized_tests.py b/GPy/testing/parameterized_tests.py
index 7b918ff9..8bfaab4e 100644
--- a/GPy/testing/parameterized_tests.py
+++ b/GPy/testing/parameterized_tests.py
@@ -7,7 +7,7 @@ import unittest
 import GPy
 import numpy as np
 from GPy.core.parameterization.parameter_core import HierarchyError
-from GPy.core.parameterization.array_core import ObsAr
+from GPy.core.parameterization.observable_array import ObsAr
 
 class ArrayCoreTest(unittest.TestCase):
     def setUp(self):
diff --git a/GPy/testing/pickle_tests.py b/GPy/testing/pickle_tests.py
index 1837f07d..fc52581a 100644
--- a/GPy/testing/pickle_tests.py
+++ b/GPy/testing/pickle_tests.py
@@ -10,7 +10,7 @@ from GPy.core.parameterization.index_operations import ParameterIndexOperations,
     ParameterIndexOperationsView
 import tempfile
 from GPy.core.parameterization.param import Param
-from GPy.core.parameterization.array_core import ObsAr
+from GPy.core.parameterization.observable_array import ObsAr
 from GPy.core.parameterization.priors import Gaussian
 from GPy.kern._src.rbf import RBF
 from GPy.kern._src.linear import Linear