diff --git a/cryptfs.h b/cryptfs.h
index 28d1887..98ba7d6 100644
--- a/cryptfs.h
+++ b/cryptfs.h
@@ -17,6 +17,8 @@
 #ifndef ANDROID_VOLD_CRYPTFS_H
 #define ANDROID_VOLD_CRYPTFS_H
 
+#include <string>
+
 #include <linux/types.h>
 #include <stdbool.h>
 #include <stdint.h>
@@ -61,7 +63,7 @@
 int cryptfs_changepw(int type, const char* newpw);
 int cryptfs_enable_default(int no_ui);
 int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, const unsigned char* key,
-                             char* out_crypto_blkdev);
+                             std::string* out_crypto_blkdev);
 int cryptfs_revert_ext_volume(const char* label);
 int cryptfs_getfield(const char* fieldname, char* value, int len);
 int cryptfs_setfield(const char* fieldname, const char* value);