diff --git a/pints/toy/_twisted_gaussian_banana.py b/pints/toy/_twisted_gaussian_banana.py
index 72544ecb7..456530c7a 100644
--- a/pints/toy/_twisted_gaussian_banana.py
+++ b/pints/toy/_twisted_gaussian_banana.py
@@ -63,10 +63,9 @@ def __init__(self, dimension=10, b=0.1, V=100):
             np.zeros(self._n_parameters), self._sigma)
 
     def __call__(self, x):
-        y = np.array(x, copy=True, dtype='float')
+        y = np.array(x, copy=True, dtype='float').reshape(self._n_parameters)
         y[0] = float(y[0]) / np.sqrt(self._V)
         y[1] += self._b * ((x[0] ** 2) - self._V)
-        y = y.reshape(self._n_parameters)
         return self._phi.logpdf(y)
 
     def distance(self, samples):