diff --git a/cmd/raidz_test/raidz_test.c b/cmd/raidz_test/raidz_test.c
index 55bfbf0ab..500ac3dae 100644
--- a/cmd/raidz_test/raidz_test.c
+++ b/cmd/raidz_test/raidz_test.c
@@ -704,7 +704,7 @@ run_sweep(void)
 
 		VERIFY3P(zk_thread_create(NULL, 0,
 		    (thread_func_t)sweep_thread,
-		    (void *) opts, TS_RUN, NULL, 0, 0,
+		    (void *) opts, 0, NULL, TS_RUN, 0,
 		    PTHREAD_CREATE_JOINABLE), !=, NULL);
 	}
 
diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index 139ff00cd..279e49fa3 100644
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -6240,7 +6240,7 @@ ztest_run(ztest_shared_t *zs)
 	 * Create a thread to periodically resume suspended I/O.
 	 */
 	VERIFY3P((resume_thread = zk_thread_create(NULL, 0,
-	    (thread_func_t)ztest_resume_thread, spa, TS_RUN, NULL, 0, 0,
+	    (thread_func_t)ztest_resume_thread, spa, 0, NULL, TS_RUN, 0,
 	    PTHREAD_CREATE_JOINABLE)), !=, NULL);
 
 #if 0
@@ -6296,7 +6296,7 @@ ztest_run(ztest_shared_t *zs)
 
 		VERIFY3P(thread = zk_thread_create(NULL, 0,
 		    (thread_func_t)ztest_thread,
-		    (void *)(uintptr_t)t, TS_RUN, NULL, 0, 0,
+		    (void *)(uintptr_t)t, 0, NULL, TS_RUN, 0,
 		    PTHREAD_CREATE_JOINABLE), !=, NULL);
 		tid[t] = thread->t_tid;
 	}
diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h
index 6e950716c..bca89e1c9 100644
--- a/include/sys/zfs_context.h
+++ b/include/sys/zfs_context.h
@@ -262,7 +262,7 @@ typedef struct kthread {
 extern kthread_t *zk_thread_current(void);
 extern void zk_thread_exit(void);
 extern kthread_t *zk_thread_create(caddr_t stk, size_t  stksize,
-	thread_func_t func, void *arg, size_t len,
+	thread_func_t func, void *arg, uint64_t len,
 	proc_t *pp, int state, pri_t pri, int detachstate);
 extern void zk_thread_join(kt_did_t tid);
 
diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index b0418cb09..40b96daba 100644
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -147,13 +147,14 @@ zk_thread_helper(void *arg)
 
 kthread_t *
 zk_thread_create(caddr_t stk, size_t stksize, thread_func_t func, void *arg,
-    size_t len, proc_t *pp, int state, pri_t pri, int detachstate)
+    uint64_t len, proc_t *pp, int state, pri_t pri, int detachstate)
 {
 	kthread_t *kt;
 	pthread_attr_t attr;
 	char *stkstr;
 
 	ASSERT0(state & ~TS_RUN);
+	ASSERT0(len);
 
 	kt = umem_zalloc(sizeof (kthread_t), UMEM_NOFAIL);
 	kt->t_func = func;