diff --git a/lib/libfdt/fdt_rw.c b/lib/libfdt/fdt_rw.c
index 93e4a2b..68887b9 100644
--- a/lib/libfdt/fdt_rw.c
+++ b/lib/libfdt/fdt_rw.c
@@ -59,7 +59,7 @@
 
 	if ((oldlen < 0) || (soff + oldlen < soff) || (soff + oldlen > dsize))
 		return -FDT_ERR_BADOFFSET;
-	if ((p < (char *)fdt) || (dsize + newlen < oldlen))
+	if ((p < (char *)fdt) || (dsize + newlen < (unsigned)oldlen))
 		return -FDT_ERR_BADOFFSET;
 	if (dsize - oldlen + newlen > fdt_totalsize(fdt))
 		return -FDT_ERR_NOSPACE;