diff --git a/epan/wslua/wslua_tvb.c b/epan/wslua/wslua_tvb.c
index d1819b70a8..0a63520694 100644
--- a/epan/wslua/wslua_tvb.c
+++ b/epan/wslua/wslua_tvb.c
@@ -883,6 +883,11 @@ WSLUA_METHOD TvbRange_nstime(lua_State* L) {
         return 0;
     }
 
+    if (encoding & ~ENC_STR_TIME_MASK) {
+        WSLUA_OPTARG_ERROR(TvbRange_nstime, ENCODING, "invalid encoding value");
+        return 0;
+    }
+
     nstime = g_new(nstime_t,1);
 
     if (encoding == 0) {
@@ -900,9 +905,6 @@ WSLUA_METHOD TvbRange_nstime(lua_State* L) {
         pushNSTime(L, nstime);
         lua_pushinteger(L, tvbr->len);
     }
-    else if (encoding & ~ENC_STR_TIME_MASK) {
-        WSLUA_OPTARG_ERROR(TvbRange_nstime, ENCODING, "invalid encoding value");
-    }
     else {
         gint endoff = 0;
         nstime_t *retval = tvb_get_string_time(tvbr->tvb->ws_tvb, tvbr->offset, tvbr->len,