--- src/nvidia_subr.c.orig	2017-01-17 00:57:56.000000000 +0500
+++ src/nvidia_subr.c	2017-08-10 23:33:44.502830000 +0500
@@ -489,7 +489,11 @@
     nv_stack_t *sp;
 
     sp = sc->api_sp;
-    rm_free_unused_clients(sp, nv, filep);
+    if (sp != NULL) {
+        rm_free_unused_clients(sp, nv, filep);
+    } else {
+        device_printf(sc->dev, "Crash prevented in nvidia_close_ctl() (FreeBSD bug 195097).\n");
+    }
 
     if (--sc->refcnt == 0) {
         NV_UMA_ZONE_FREE_STACK(sc->api_sp);
@@ -594,9 +599,15 @@
 
     sc = nv->os_state;
     sp = sc->api_sp;
+    /* If nvidia_open_dev failed and we're called from nvidia_dev_dtor, we
+     * already released api_sp. */
 
     NV_PCI_CHECK_CONFIG_SPACE(sp, nv, TRUE, TRUE, TRUE);
-    rm_free_unused_clients(sp, nv, filep);
+    if (sp != NULL) {
+        rm_free_unused_clients(sp, nv, filep);
+    } else {
+        device_printf(sc->dev, "Crash prevented in nvidia_close_dev() (FreeBSD bug 195097).\n");
+    }
 
     if (--sc->refcnt == 0) {
         if (sc->UD_object != NULL)