diff --git a/tests/unittests/torture_keyfiles.c b/tests/unittests/torture_keyfiles.c
index 0dd3bce4..de924f00 100644
--- a/tests/unittests/torture_keyfiles.c
+++ b/tests/unittests/torture_keyfiles.c
@@ -140,6 +140,7 @@ static int torture_read_one_line(const char *filename, char *buffer, size_t len)
     fclose(fp);
     return -1;
   }
+  buffer[len - 1] = '\0';
 
   fclose(fp);