diff --git a/lib/libfdt/fdt_wip.c b/lib/libfdt/fdt_wip.c
index f64139e..c2d7566 100644
--- a/lib/libfdt/fdt_wip.c
+++ b/lib/libfdt/fdt_wip.c
@@ -23,7 +23,7 @@
 	if (!propval)
 		return proplen;
 
-	if (proplen < (len + idx))
+	if ((unsigned)proplen < (len + idx))
 		return -FDT_ERR_NOSPACE;
 
 	memcpy((char *)propval + idx, val, len);