diff -ur emcee-2.2.1/emcee/tests.py emcee-2.2.1.btest/emcee/tests.py
--- emcee-2.2.1/emcee/tests.py	2016-07-15 10:12:21.000000000 +0200
+++ emcee-2.2.1.btest/emcee/tests.py	2019-07-11 11:48:15.264302724 +0200
@@ -178,7 +178,7 @@
 
         # If a walker is right at zero, ``lnprobfn`` returns ``np.nan``.
         p0 = self.p0
-        p0[0] = 0.0
+        p0[0] = np.zeros_like(p0[0])
 
         try:
             self.check_sampler(p0=p0)