diff --git a/src/xml/xml_native_reader.cc b/src/xml/xml_native_reader.cc
index 120fbda7..ebd674ef 100644
--- a/src/xml/xml_native_reader.cc
+++ b/src/xml/xml_native_reader.cc
@@ -3186,8 +3186,9 @@ void mjXReader::Sensor(XMLElement* section) {
       if (psen->objtype == mjOBJ_UNKNOWN && !psen->objname.empty()) {
         throw mjXError(elem, "objname is specified but objtype is not");
       }
-      ReadAttrTxt(elem, "reftype", text);
-      psen->reftype = (mjtObj)mju_str2Type(text.c_str());
+      if (ReadAttrTxt(elem, "reftype", text)) {
+        psen->reftype = (mjtObj)mju_str2Type(text.c_str());
+      }
       ReadAttrTxt(elem, "refname", psen->refname);
       if (psen->reftype != mjOBJ_UNKNOWN && psen->refname.empty()) {
         throw mjXError(elem, "reftype is specified but refname is not");