diff --git a/libfdt/libfdt_internal.h b/libfdt/libfdt_internal.h
index 9eb3239..0e103ca 100644
--- a/libfdt/libfdt_internal.h
+++ b/libfdt/libfdt_internal.h
@@ -11,11 +11,13 @@
 #define FDT_TAGALIGN(x)		(FDT_ALIGN((x), FDT_TAGSIZE))
 
 int32_t fdt_ro_probe_(const void *fdt);
-#define FDT_RO_PROBE(fdt)					\
-	{							\
-		int32_t totalsize_;				\
-		if ((totalsize_ = fdt_ro_probe_(fdt)) < 0)	\
-			return totalsize_;			\
+#define FDT_RO_PROBE(fdt)						\
+	{								\
+		if (!can_assume(VALID_DTB)) {				\
+			int32_t totalsize_;				\
+			if ((totalsize_ = fdt_ro_probe_(fdt)) < 0)	\
+				return totalsize_;			\
+		}							\
 	}
 
 int fdt_check_node_offset_(const void *fdt, int offset);