diff --git a/kmod/src/Makefile b/kmod/src/Makefile
index 5b824081..889f80d7 100644
--- a/kmod/src/Makefile
+++ b/kmod/src/Makefile
@@ -7,3 +7,18 @@ CFLAGS_scoutfs_trace.o = -I$(src) # define_trace.h double include
 scoutfs-y += alloc.o bio.o btree.o compact.o counters.o data.o dir.o kvec.o \
 	     inode.o ioctl.o item.o key.o lock.o manifest.o msg.o net.o \
 	     options.o seg.o scoutfs_trace.o sort_priv.o super.o trans.o xattr.o
+
+#
+# The raw types aren't available in userspace headers.  Make sure all
+# the types we use in the headers are the exported __ versions.
+#
+# XXX dunno how we're really supposed to do this in kbuild
+#
+.PHONY: $(src)/check_exported_types
+$(src)/check_exported_types:
+	@if egrep '\<[us](8|16|32|64\>)' $(src)/format.h $(src)/ioctl.h; then \
+		echo "no raw types in exported headers, preface with __";     \
+		exit 1;							      \
+	fi
+
+extra-y += check_exported_types
diff --git a/kmod/src/format.h b/kmod/src/format.h
index 6251c8f8..6c37816d 100644
--- a/kmod/src/format.h
+++ b/kmod/src/format.h
@@ -212,8 +212,8 @@ struct scoutfs_segment_item {
 	__u8 nr_links;
 	__le32 skip_links[0];
 	/*
-	 * u8 key_bytes[key_len]
-	 * u8 val_bytes[val_len]
+	 * __u8 key_bytes[key_len]
+	 * __u8 val_bytes[val_len]
 	 */
 } __packed;
 
diff --git a/kmod/src/ioctl.h b/kmod/src/ioctl.h
index 79241e9f..0dcb6bc7 100644
--- a/kmod/src/ioctl.h
+++ b/kmod/src/ioctl.h
@@ -116,7 +116,7 @@ struct scoutfs_ioctl_ino_path {
 } __packed;
 
 #define SCOUTFS_IOC_INO_PATH_CURSOR_BYTES \
-	(sizeof(u64) + SCOUTFS_NAME_LEN + 1)
+	(sizeof(__u64) + SCOUTFS_NAME_LEN + 1)
 
 /* Get a single path from the root to the given inode number */
 #define SCOUTFS_IOC_INO_PATH _IOW(SCOUTFS_IOCTL_MAGIC, 2, \