diff --git a/client/fwknop_common.h b/client/fwknop_common.h
index 600b9eb8..3c526df1 100644
--- a/client/fwknop_common.h
+++ b/client/fwknop_common.h
@@ -103,10 +103,10 @@ typedef struct fko_cli_options
     /* Encryption keys read from a .fwknoprc stanza
     */
     char key[MAX_KEY_LEN+1];
-    char key_base64[2*MAX_KEY_LEN+1];
+    char key_base64[MAX_B64_KEY_LEN+1];
     int  key_len;
     char hmac_key[MAX_KEY_LEN+1];
-    char hmac_key_base64[2*MAX_KEY_LEN+1];
+    char hmac_key_base64[MAX_B64_KEY_LEN+1];
     int  hmac_key_len;
     int  have_key;
     int  have_base64_key;