diff --git a/hw/core/loader.c b/hw/core/loader.c
index fe5cb24122..a097bbe30a 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -1025,6 +1025,7 @@ MemoryRegion *rom_add_blob(const char *name, const void *blob, size_t len,
     rom->addr     = addr;
     rom->romsize  = max_len ? max_len : len;
     rom->datasize = len;
+    g_assert(rom->romsize >= rom->datasize);
     rom->data     = g_malloc0(rom->datasize);
     memcpy(rom->data, blob, len);
     rom_insert(rom);