diff --git a/blkmaker_jansson.c b/blkmaker_jansson.c
index 5c87650..c085d99 100644
--- a/blkmaker_jansson.c
+++ b/blkmaker_jansson.c
@@ -162,7 +162,7 @@ void my_flip(void *data, size_t datasz) {
 	}
 }
 
-const char *blktmpl_add_jansson(blktemplate_t *tmpl, json_t *json, time_t time_rcvd) {
+const char *blktmpl_add_jansson(blktemplate_t *tmpl, const json_t *json, time_t time_rcvd) {
 	if (tmpl->version)
 		return false;
 	
diff --git a/blkmaker_jansson.h b/blkmaker_jansson.h
index e3fe0cd..4a0a872 100644
--- a/blkmaker_jansson.h
+++ b/blkmaker_jansson.h
@@ -6,7 +6,7 @@
 #include <blktemplate.h>
 
 extern json_t *blktmpl_request_jansson(gbt_capabilities_t extracaps);
-extern const char *blktmpl_add_jansson(blktemplate_t *, json_t *, time_t time_rcvd);
+extern const char *blktmpl_add_jansson(blktemplate_t *, const json_t *, time_t time_rcvd);
 extern json_t *blkmk_submit_jansson(blktemplate_t *, const unsigned char *data, blknonce_t);
 
 #endif