diff --git a/audio/out/ao_oss.c b/audio/out/ao_oss.c
index 3f85774d02..2d1a60db4d 100644
--- a/audio/out/ao_oss.c
+++ b/audio/out/ao_oss.c
@@ -116,7 +116,7 @@ static void device_descr_get(size_t dev_idx, char *buf, size_t buf_size)
     snprintf(dev_path, sizeof(dev_path), PATH_DEV_MIXER"%zu", dev_idx);
     int fd = open(dev_path, O_RDONLY);
     if (ioctl(fd, SOUND_MIXER_INFO, &mi) == 0) {
-        strncpy(buf, mi.name, buf_size);
+        strncpy(buf, mi.name, buf_size - 1);
         tmp = (buf_size - 1);
     }
     close(fd);
diff --git a/video/out/d3d11/ra_d3d11.c b/video/out/d3d11/ra_d3d11.c
index a9c2f0b163..62fcc1f47e 100644
--- a/video/out/d3d11/ra_d3d11.c
+++ b/video/out/d3d11/ra_d3d11.c
@@ -1597,8 +1597,8 @@ static void save_cached_program(struct ra *ra, struct ra_renderpass *pass,
         .frag_bytecode_len = frag_bc.len,
         .comp_bytecode_len = comp_bc.len,
     };
-    strncpy(header.magic, cache_magic, sizeof(header.magic));
-    strncpy(header.compiler, spirv->name, sizeof(header.compiler));
+    memcpy(header.magic, cache_magic, sizeof(header.magic));
+    strncpy(header.compiler, spirv->name, sizeof(header.compiler) - 1);
 
     struct bstr *prog = &pass->params.cached_program;
     bstr_xappend(pass, prog, (bstr){ (char *) &header, sizeof(header) });