diff --git a/libfreefare/mifare_desfire_error.c b/libfreefare/mifare_desfire_error.c
index 9f4888e..87a661b 100644
--- a/libfreefare/mifare_desfire_error.c
+++ b/libfreefare/mifare_desfire_error.c
@@ -30,7 +30,7 @@
 
 static struct error_message {
     uint8_t code;
-    char *message;
+    const char *message;
 } error_messages[] = {
     EM(OPERATION_OK),
     EM(NO_CHANGES),