diff --git a/tools/libs/light/libxl_utils.c b/tools/libs/light/libxl_utils.c
index e403bd9bcf..01eb3a3670 100644
--- a/tools/libs/light/libxl_utils.c
+++ b/tools/libs/light/libxl_utils.c
@@ -45,7 +45,7 @@ unsigned long libxl_get_required_shadow_memory(unsigned long maxmem_kb, unsigned
 char *libxl_domid_to_name(libxl_ctx *ctx, uint32_t domid)
 {
     unsigned int len;
-    char path[strlen("/local/domain") + 12];
+    char path[sizeof("/local/domain") + 11];
     char *s;
 
     snprintf(path, sizeof(path), "/local/domain/%d/name", domid);
@@ -141,7 +141,7 @@ int libxl_cpupool_qualifier_to_cpupoolid(libxl_ctx *ctx, const char *p,
 char *libxl_cpupoolid_to_name(libxl_ctx *ctx, uint32_t poolid)
 {
     unsigned int len;
-    char path[strlen("/local/pool") + 12];
+    char path[sizeof("/local/pool") + 11];
     char *s;
 
     snprintf(path, sizeof(path), "/local/pool/%d/name", poolid);