diff --git a/zeus/ensemble.py b/zeus/ensemble.py
index 4242d87..368986a 100644
--- a/zeus/ensemble.py
+++ b/zeus/ensemble.py
@@ -494,6 +494,9 @@ def sample(self,
         if not np.all(np.isfinite(Z)):
             raise ValueError('Invalid walker initial positions! \n' +
                              'Initialise walkers from positions of finite log probability.')
+        if self.nwalkers > 1 and (X == X[0]).all():
+            raise ValueError('Invalid walker initial positions! \n' +
+                             'Initialise walkers from different starting positions.')
         batch = list(np.arange(self.nwalkers))
 
         # Extend saving space
@@ -724,4 +727,4 @@ def sample(self,
 class sampler(EnsembleSampler):
     def __init__(self, *args, **kwargs):
         logging.warning('The sampler class has been deprecated. Please use the new EnsembleSampler class.')
-        super().__init__(*args, **kwargs)
\ No newline at end of file
+        super().__init__(*args, **kwargs)