diff --git a/src/sasl.c b/src/sasl.c
index 73fbbc9..6fe0e00 100644
--- a/src/sasl.c
+++ b/src/sasl.c
@@ -552,8 +552,8 @@ unsigned char *base64_decode(xmpp_ctx_t *ctx,
 		if (hextet != 64) goto _base64_decode_error;
 		break;
 	}
+	*d = '\0';
     }
-    *d = '\0';
     return dbuf;
 
 _base64_decode_error: