diff --git a/halo2_proofs/src/plonk/circuit.rs b/halo2_proofs/src/plonk/circuit.rs
index ee837585f2..59f2301bde 100644
--- a/halo2_proofs/src/plonk/circuit.rs
+++ b/halo2_proofs/src/plonk/circuit.rs
@@ -1590,8 +1590,8 @@ pub struct LookupTracker<F: Field> {
     pub(crate) inputs: Vec<Vec<Expression<F>>>,
 }
 
-impl<F: Field> fmt::Debug for LookupTracker<F> where F: fmt::Debug {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+impl<F: Field> std::fmt::Debug for LookupTracker<F> where F: std::fmt::Debug {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("LookupTracker")
             .field("table", &self.table)
             .field("inputs", &self.inputs)