diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-06-07-20-18-38.bpo-33803.n-Nq6_.rst b/Misc/NEWS.d/next/Core and Builtins/2018-06-07-20-18-38.bpo-33803.n-Nq6_.rst
new file mode 100644
index 0000000..9cb8457
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-06-07-20-18-38.bpo-33803.n-Nq6_.rst
@@ -0,0 +1,2 @@
+Fix a crash in hamt.c caused by enabling GC tracking for an object that
+hadn't all of its fields set to NULL.
diff --git a/Python/hamt.c b/Python/hamt.c
index 5217122..f8bce59 100644
--- a/Python/hamt.c
+++ b/Python/hamt.c
@@ -2476,6 +2476,8 @@
     if (o == NULL) {
         return NULL;
     }
+    o->h_count = 0;
+    o->h_root = NULL;
     o->h_weakreflist = NULL;
     PyObject_GC_Track(o);
     return o;