diff --git a/src/json.c b/src/json.c
index bfa5d50..770e144 100644
--- a/src/json.c
+++ b/src/json.c
@@ -215,7 +215,7 @@
 
 	case VAR_NUMBER:
 	    vim_snprintf((char *)numbuf, NUMBUFLEN, "%lld",
-					      (long_long_T)val->vval.v_number);
+					      (varnumber_T)val->vval.v_number);
 	    ga_concat(gap, numbuf);
 	    break;