diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 825996408465..3e7c8ad5bed9 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3634,6 +3634,14 @@ static bool is_unsync_root(hpa_t root)
 	 */
 	smp_rmb();
 	sp = to_shadow_page(root);
+
+	/*
+	 * PAE roots (somewhat arbitrarily) aren't backed by shadow pages, the
+	 * PDPTEs for a given PAE root need to be synchronized individually.
+	 */
+	if (WARN_ON_ONCE(!sp))
+		return false;
+
 	if (sp->unsync || sp->unsync_children)
 		return true;