diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index d8d8e7b..eb1cc92 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -110,6 +110,7 @@
 	int sub_version;
 	int min_proto;
 	int max_proto;
+	int compat_daemon;
 	unsigned long exp_timeout;
 	unsigned int type;
 	int reghost_enabled;
diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 76741d8..85f1fcd 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -385,6 +385,7 @@
 		sbi->pipefd = pipefd;
 		sbi->pipe = pipe;
 		sbi->catatonic = 0;
+		sbi->compat_daemon = is_compat_task();
 	}
 out:
 	mutex_unlock(&sbi->wq_mutex);
diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
index e16980b..06858d9 100644
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -19,6 +19,7 @@
 #include <linux/parser.h>
 #include <linux/bitops.h>
 #include <linux/magic.h>
+#include <linux/compat.h>
 #include "autofs_i.h"
 #include <linux/module.h>
 
@@ -224,6 +225,7 @@
 	set_autofs_type_indirect(&sbi->type);
 	sbi->min_proto = 0;
 	sbi->max_proto = 0;
+	sbi->compat_daemon = is_compat_task();
 	mutex_init(&sbi->wq_mutex);
 	mutex_init(&sbi->pipe_mutex);
 	spin_lock_init(&sbi->fs_lock);
diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index da8876d..9c098db 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -91,7 +91,24 @@
 
 	return (bytes > 0);
 }
-	
+
+/*
+ * The autofs_v5 packet was misdesigned.
+ *
+ * The packets are identical on x86-32 and x86-64, but have different
+ * alignment. Which means that 'sizeof()' will give different results.
+ * Fix it up for the case of running 32-bit user mode on a 64-bit kernel.
+ */
+static noinline size_t autofs_v5_packet_size(struct autofs_sb_info *sbi)
+{
+	size_t pktsz = sizeof(struct autofs_v5_packet);
+#if defined(CONFIG_X86_64) && defined(CONFIG_COMPAT)
+	if (sbi->compat_daemon > 0)
+		pktsz -= 4;
+#endif
+	return pktsz;
+}
+
 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
 				 struct autofs_wait_queue *wq,
 				 int type)
@@ -155,8 +172,7 @@
 	{
 		struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 
-		pktsz = sizeof(*packet);
-
+		pktsz = autofs_v5_packet_size(sbi);
 		packet->wait_queue_token = wq->wait_queue_token;
 		packet->len = wq->name.len;
 		memcpy(packet->name, wq->name.name, wq->name.len);