diff --git a/Python/pystate.c b/Python/pystate.c
index fed1df0173bacf..e0030bf136e05a 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -1505,6 +1505,7 @@ alloc_threadstate(PyInterpreterState *interp)
         }
         reset_threadstate(tstate);
     }
+    tstate->base.interp = interp;
     return tstate;
 }