diff --git a/usr.bin/dtc/fdt.cc b/usr.bin/dtc/fdt.cc
index 41c627d3fd9..16ebfd1fa3d 100644
--- a/usr.bin/dtc/fdt.cc
+++ b/usr.bin/dtc/fdt.cc
@@ -1635,7 +1635,7 @@ device_tree::parse_dts(const string &fn, FILE *depfile)
 
 bool device_tree::parse_define(const char *def)
 {
-	char *val = strchr(def, '=');
+	const char *val = strchr(def, '=');
 	if (!val)
 	{
 		if (strlen(def) != 0)