diff --git a/sys/compat/linuxkpi/common/include/linux/kernel.h b/sys/compat/linuxkpi/common/include/linux/kernel.h
--- a/sys/compat/linuxkpi/common/include/linux/kernel.h
+++ b/sys/compat/linuxkpi/common/include/linux/kernel.h
@@ -465,6 +465,12 @@
        return (0);
 }
 
+static inline int
+kstrtoull(const char *cp, unsigned int base, unsigned long long *res)
+{
+	return (kstrtou64(cp, base, (u64 *)res));
+}
+
 static inline int
 kstrtobool(const char *s, bool *res)
 {