diff --git a/EncryptInplace.h b/EncryptInplace.h
index 71644ac..bf0c314 100644
--- a/EncryptInplace.h
+++ b/EncryptInplace.h
@@ -24,7 +24,7 @@
 #define RETRY_MOUNT_ATTEMPTS 10
 #define RETRY_MOUNT_DELAY_SECONDS 1
 
-int cryptfs_enable_inplace(char* crypto_blkdev, char* real_blkdev, off64_t size,
+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);