diff --git a/config/kernel-user-ns-inum.m4 b/config/kernel-user-ns-inum.m4
deleted file mode 100644
index 2207a4aa6..000000000
--- a/config/kernel-user-ns-inum.m4
+++ /dev/null
@@ -1,23 +0,0 @@
-dnl #
-dnl # 3.18 API change
-dnl # struct user_namespace inum moved from .proc_inum to .ns.inum.
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_SRC_USER_NS_COMMON_INUM], [
-	ZFS_LINUX_TEST_SRC([user_ns_common_inum], [
-		#include <linux/user_namespace.h>
-	], [
-		struct user_namespace uns;
-		uns.ns.inum = 0;
-	])
-])
-
-AC_DEFUN([ZFS_AC_KERNEL_USER_NS_COMMON_INUM], [
-	AC_MSG_CHECKING([whether user_namespace->ns.inum exists])
-	ZFS_LINUX_TEST_RESULT([user_ns_common_inum], [
-		AC_MSG_RESULT(yes)
-		AC_DEFINE(HAVE_USER_NS_COMMON_INUM, 1,
-		    [user_namespace->ns.inum exists])
-	],[
-		AC_MSG_RESULT(no)
-	])
-])
diff --git a/config/kernel.m4 b/config/kernel.m4
index 68329afed..803a95c06 100644
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -146,7 +146,6 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_KTHREAD
 	ZFS_AC_KERNEL_SRC_ZERO_PAGE
 	ZFS_AC_KERNEL_SRC___COPY_FROM_USER_INATOMIC
-	ZFS_AC_KERNEL_SRC_USER_NS_COMMON_INUM
 	ZFS_AC_KERNEL_SRC_IDMAP_MNT_API
 	ZFS_AC_KERNEL_SRC_IDMAP_NO_USERNS
 	ZFS_AC_KERNEL_SRC_IATTR_VFSID
@@ -288,7 +287,6 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_KTHREAD
 	ZFS_AC_KERNEL_ZERO_PAGE
 	ZFS_AC_KERNEL___COPY_FROM_USER_INATOMIC
-	ZFS_AC_KERNEL_USER_NS_COMMON_INUM
 	ZFS_AC_KERNEL_IDMAP_MNT_API
 	ZFS_AC_KERNEL_IDMAP_NO_USERNS
 	ZFS_AC_KERNEL_IATTR_VFSID
diff --git a/module/os/linux/spl/spl-zone.c b/module/os/linux/spl/spl-zone.c
index d0d0cca15..58b5e0dc4 100644
--- a/module/os/linux/spl/spl-zone.c
+++ b/module/os/linux/spl/spl-zone.c
@@ -54,7 +54,7 @@ typedef struct zone_dataset {
 	char zd_dsname[];		/* name of the member dataset */
 } zone_dataset_t;
 
-#if defined(CONFIG_USER_NS) && defined(HAVE_USER_NS_COMMON_INUM)
+#ifdef CONFIG_USER_NS
 /*
  * Returns:
  * - 0 on success
@@ -95,18 +95,14 @@ done:
 
 	return (error);
 }
-#endif /* defined(CONFIG_USER_NS) && defined(HAVE_USER_NS_COMMON_INUM) */
+#endif /* CONFIG_USER_NS */
 
 static unsigned int
 user_ns_zoneid(struct user_namespace *user_ns)
 {
 	unsigned int r;
 
-#if defined(HAVE_USER_NS_COMMON_INUM)
 	r = user_ns->ns.inum;
-#else
-	r = user_ns->proc_inum;
-#endif
 
 	return (r);
 }
@@ -123,7 +119,7 @@ zone_datasets_lookup(unsigned int nsinum)
 	return (NULL);
 }
 
-#if defined(CONFIG_USER_NS) && defined(HAVE_USER_NS_COMMON_INUM)
+#ifdef CONFIG_USER_NS
 static struct zone_dataset *
 zone_dataset_lookup(zone_datasets_t *zds, const char *dataset, size_t dsnamelen)
 {
@@ -148,7 +144,7 @@ zone_dataset_cred_check(cred_t *cred)
 
 	return (0);
 }
-#endif /* defined(CONFIG_USER_NS) && defined(HAVE_USER_NS_COMMON_INUM) */
+#endif /* CONFIG_USER_NS */
 
 static int
 zone_dataset_name_check(const char *dataset, size_t *dsnamelen)
@@ -168,7 +164,7 @@ zone_dataset_name_check(const char *dataset, size_t *dsnamelen)
 int
 zone_dataset_attach(cred_t *cred, const char *dataset, int userns_fd)
 {
-#if defined(CONFIG_USER_NS) && defined(HAVE_USER_NS_COMMON_INUM)
+#ifdef CONFIG_USER_NS
 	struct user_namespace *userns;
 	zone_datasets_t *zds;
 	zone_dataset_t *zd;
@@ -213,14 +209,14 @@ zone_dataset_attach(cred_t *cred, const char *dataset, int userns_fd)
 	return (0);
 #else
 	return (ENXIO);
-#endif /* defined(CONFIG_USER_NS) && defined(HAVE_USER_NS_COMMON_INUM) */
+#endif /* CONFIG_USER_NS */
 }
 EXPORT_SYMBOL(zone_dataset_attach);
 
 int
 zone_dataset_detach(cred_t *cred, const char *dataset, int userns_fd)
 {
-#if defined(CONFIG_USER_NS) && defined(HAVE_USER_NS_COMMON_INUM)
+#ifdef CONFIG_USER_NS
 	struct user_namespace *userns;
 	zone_datasets_t *zds;
 	zone_dataset_t *zd;
@@ -262,7 +258,7 @@ zone_dataset_detach(cred_t *cred, const char *dataset, int userns_fd)
 	return (0);
 #else
 	return (ENXIO);
-#endif /* defined(CONFIG_USER_NS) && defined(HAVE_USER_NS_COMMON_INUM) */
+#endif /* CONFIG_USER_NS */
 }
 EXPORT_SYMBOL(zone_dataset_detach);