diff --git a/src/iop/generator.rs b/src/iop/generator.rs
index 17567a4c..6ab1b412 100644
--- a/src/iop/generator.rs
+++ b/src/iop/generator.rs
@@ -1,3 +1,4 @@
+use std::convert::identity;
 use std::fmt::Debug;
 
 use crate::field::extension_field::target::ExtensionTarget;
@@ -74,6 +75,11 @@ pub(crate) fn generate_partial_witness<F: Field>(
 
         pending_generator_indices = next_pending_generator_indices;
     }
+
+    assert!(
+        generator_is_expired.into_iter().all(identity),
+        "Some generators weren't run."
+    );
 }
 
 /// A generator participates in the generation of the witness.
diff --git a/src/plonk/circuit_builder.rs b/src/plonk/circuit_builder.rs
index 573e0532..8afec0e4 100644
--- a/src/plonk/circuit_builder.rs
+++ b/src/plonk/circuit_builder.rs
@@ -8,6 +8,7 @@ use crate::field::cosets::get_unique_coset_shifts;
 use crate::field::extension_field::target::ExtensionTarget;
 use crate::field::extension_field::{Extendable, FieldExtension};
 use crate::fri::commitment::PolynomialBatchCommitment;
+use crate::gates::arithmetic::{ArithmeticExtensionGate, NUM_ARITHMETIC_OPS};
 use crate::gates::constant::ConstantGate;
 use crate::gates::gate::{Gate, GateInstance, GateRef, PrefixedGate};
 use crate::gates::gate_tree::Tree;
@@ -527,6 +528,33 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         wire_partition.get_sigma_polys(degree_log, k_is, subgroup)
     }
 
+    /// Fill the remaining unused arithmetic operations with zeros, so that all
+    /// `ArithmeticExtensionGenerator` are run.
+    fn fill_arithmetic_gates(&mut self) {
+        let zero = self.zero_extension();
+        let remaining_arithmetic_gates = self.free_arithmetic.values().copied().collect::<Vec<_>>();
+        for (gate, i) in remaining_arithmetic_gates {
+            for j in i..NUM_ARITHMETIC_OPS {
+                let wires_multiplicand_0 = ExtensionTarget::from_range(
+                    gate,
+                    ArithmeticExtensionGate::<D>::wires_ith_multiplicand_0(j),
+                );
+                let wires_multiplicand_1 = ExtensionTarget::from_range(
+                    gate,
+                    ArithmeticExtensionGate::<D>::wires_ith_multiplicand_1(j),
+                );
+                let wires_addend = ExtensionTarget::from_range(
+                    gate,
+                    ArithmeticExtensionGate::<D>::wires_ith_addend(j),
+                );
+
+                self.route_extension(zero, wires_multiplicand_0);
+                self.route_extension(zero, wires_multiplicand_1);
+                self.route_extension(zero, wires_addend);
+            }
+        }
+    }
+
     pub fn print_gate_counts(&self, min_delta: usize) {
         self.context_log
             .filter(self.num_gates(), min_delta)
@@ -538,6 +566,8 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         let mut timing = TimingTree::new("preprocess", Level::Trace);
         let start = Instant::now();
 
+        self.fill_arithmetic_gates();
+
         // Hash the public inputs, and route them to a `PublicInputGate` which will enforce that
         // those hash wires match the claimed public inputs.
         let public_inputs_hash = self.hash_n_to_hash(self.public_inputs.clone(), true);