diff --git a/src/r1cs_var.rs b/src/r1cs_var.rs
index dcbe5c9a..4562223b 100644
--- a/src/r1cs_var.rs
+++ b/src/r1cs_var.rs
@@ -1,4 +1,5 @@
 use ark_ff::Field;
+use ark_std::vec::Vec;
 use ark_relations::r1cs::{ConstraintSystemRef, SynthesisError};
 
 /// This trait describes some core functionality that is common to high-level