diff --git a/backend/src/estark/starky_wrapper.rs b/backend/src/estark/starky_wrapper.rs
index 6ba9d715e..c94c9908c 100644
--- a/backend/src/estark/starky_wrapper.rs
+++ b/backend/src/estark/starky_wrapper.rs
@@ -1,7 +1,7 @@
+use std::io;
 use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::Instant;
-use std::{borrow::Cow, io};
 
 use crate::{Backend, BackendFactory, BackendOptions, Error};
 use powdr_ast::analyzed::Analyzed;
@@ -47,15 +47,13 @@ impl<F: FieldElement> BackendFactory<F> for Factory {
             return Err(Error::NoAggregationAvailable);
         }
 
-        let fixed = (*fixed).clone();
-
         let proof_type: ProofType = ProofType::from(options);
 
         let params = create_stark_struct(pil.degree(), proof_type.hash_type());
 
         let (pil_json, patched_fixed) = first_step_fixup(&pil, &fixed);
 
-        let fixed = patched_fixed.map_or_else(|| Cow::Borrowed(&fixed), Cow::Owned);
+        let fixed = patched_fixed.map_or_else(|| fixed.clone(), Arc::new);
 
         let const_pols = to_starky_pols_array(&fixed, &pil_json, PolKind::Constant);
 
@@ -66,7 +64,7 @@ impl<F: FieldElement> BackendFactory<F> for Factory {
         };
 
         Ok(Box::new(EStark {
-            fixed: fixed.to_vec(),
+            fixed,
             pil_json,
             params,
             setup,
@@ -90,7 +88,7 @@ fn create_stark_setup(
 }
 
 pub struct EStark<F: FieldElement> {
-    fixed: Vec<(String, Vec<F>)>,
+    fixed: Arc<Vec<(String, Vec<F>)>>,
     pil_json: PIL,
     params: StarkStruct,
     // eSTARK calls it setup, but it works similarly to a verification key and depends only on the