diff --git a/generic/cursor.c b/generic/cursor.c
index 1a24c1c..eecb0f9 100644
--- a/generic/cursor.c
+++ b/generic/cursor.c
@@ -170,17 +170,21 @@ mongotcl_tcllist_to_cursor_fields (Tcl_Interp *interp, Tcl_Obj *fieldList, mongo
 		char *key = Tcl_GetString (listObjv[i]);
 
 		if (Tcl_GetIntFromObj (interp, listObjv[i+1], &want) == TCL_ERROR) {
-		  error:
-			bson_destroy(mc->fieldsBson);
-			return TCL_ERROR;
+		  bson_error:
+			return mongotcl_setBsonError (interp, mc->fieldsBson);
 		}
 
 		if (bson_append_int (mc->fieldsBson, key, want) != BSON_OK) {
-			Tcl_SetObjResult (interp, Tcl_NewStringObj ("bson error while generating field list", -1));
-			goto error;
+			goto bson_error;
 		}
 	}
 
+	if (bson_finish (mc->fieldsBson) != BSON_OK) {
+		goto bson_error;
+	}
+
+	mongo_cursor_set_fields (mc->cursor, mc->fieldsBson);
+
 	return TCL_OK;
 }
 
diff --git a/generic/mongotcl.h b/generic/mongotcl.h
index 3b93ad9..d3996d7 100644
--- a/generic/mongotcl.h
+++ b/generic/mongotcl.h
@@ -44,6 +44,9 @@ mongotcl_setMongoError (Tcl_Interp *interp, mongo *conn);
 extern int
 mongotcl_create_bson_command (Tcl_Interp *interp, char *commandName, CONST bson *bsonObj);
 
+extern int
+mongotcl_setBsonError (Tcl_Interp *interp, bson *bson);
+
 extern int
 mongotcl_createCursorObjCmd(Tcl_Interp *interp, mongo *conn, char *commandName, char *namespace); ;