diff --git a/src/xz/message.c b/src/xz/message.c
index ad93573a..6eed5f7e 100644
--- a/src/xz/message.c
+++ b/src/xz/message.c
@@ -912,8 +912,8 @@ message_filters_to_str(const lzma_filter *filters, bool all_known)
 		case LZMA_FILTER_LZMA1:
 		case LZMA_FILTER_LZMA2: {
 			const lzma_options_lzma *opt = filters[i].options;
-			const char *mode;
-			const char *mf;
+			const char *mode = NULL;
+			const char *mf = NULL;
 
 			if (all_known) {
 				switch (opt->mode) {