diff --git a/EncryptInplace.h b/EncryptInplace.h
index bf0c314..a2b46cf 100644
--- a/EncryptInplace.h
+++ b/EncryptInplace.h
@@ -24,6 +24,11 @@
 #define RETRY_MOUNT_ATTEMPTS 10
 #define RETRY_MOUNT_DELAY_SECONDS 1
 
+/* Return values for cryptfs_enable_inplace() */
+#define ENABLE_INPLACE_OK 0
+#define ENABLE_INPLACE_ERR_OTHER (-1)
+#define ENABLE_INPLACE_ERR_DEV (-2) /* crypto_blkdev issue */
+
 int cryptfs_enable_inplace(const char* crypto_blkdev, const char* real_blkdev, off64_t size,
                            off64_t* size_already_done, off64_t tot_size,
                            off64_t previously_encrypted_upto, bool set_progress_properties);