diff --git a/include/polarssl/padlock.h b/include/polarssl/padlock.h
index 4cc6be2..cde76ae 100644
--- a/include/polarssl/padlock.h
+++ b/include/polarssl/padlock.h
@@ -63,7 +63,7 @@
  */
 int padlock_xcryptecb( aes_context *ctx,
                        int mode,
-                       unsigned char input[16],
+                       const unsigned char input[16],
                        unsigned char output[16] );
 
 /**
@@ -82,7 +82,7 @@
                        int mode,
                        int length,
                        unsigned char iv[16],
-                       unsigned char *input,
+                       const unsigned char *input,
                        unsigned char *output );
 
 #ifdef __cplusplus