diff --git a/wheel/src/run_generator.rs b/wheel/src/run_generator.rs
index bc364728b..00be27e35 100644
--- a/wheel/src/run_generator.rs
+++ b/wheel/src/run_generator.rs
@@ -20,7 +20,7 @@ pub fn py_to_slice<'a>(buf: PyBuffer<u8>) -> &'a [u8] {
 
 #[pyfunction]
 pub fn run_block_generator<'a>(
-    _py: Python<'a>,
+    py: Python<'a>,
     program: PyBuffer<u8>,
     block_refs: &Bound<'_, PyList>,
     max_cost: Cost,
@@ -29,12 +29,15 @@ pub fn run_block_generator<'a>(
 ) -> (Option<u32>, Option<OwnedSpendBundleConditions>) {
     let mut allocator = make_allocator(flags);
 
-    let refs = block_refs.into_iter().map(|b| {
-        let buf = b
-            .extract::<PyBuffer<u8>>()
-            .expect("block_refs should be a list of buffers");
-        py_to_slice::<'a>(buf)
-    });
+    let refs = block_refs
+        .into_iter()
+        .map(|b| {
+            let buf = b
+                .extract::<PyBuffer<u8>>()
+                .expect("block_refs should be a list of buffers");
+            py_to_slice::<'a>(buf)
+        })
+        .collect::<Vec<&'a [u8]>>();
     let program = py_to_slice::<'a>(program);
     let run_block = if (flags & ANALYZE_SPENDS) == 0 {
         native_run_block_generator::<_, EmptyVisitor, _>
@@ -42,24 +45,26 @@ pub fn run_block_generator<'a>(
         native_run_block_generator::<_, MempoolVisitor, _>
     };
 
-    match run_block(&mut allocator, program, refs, max_cost, flags, constants) {
-        Ok(spend_bundle_conds) => (
-            None,
-            Some(OwnedSpendBundleConditions::from(
-                &allocator,
-                spend_bundle_conds,
-            )),
-        ),
-        Err(ValidationErr(_, error_code)) => {
-            // a validation error occurred
-            (Some(error_code.into()), None)
+    py.allow_threads(|| {
+        match run_block(&mut allocator, program, refs, max_cost, flags, constants) {
+            Ok(spend_bundle_conds) => (
+                None,
+                Some(OwnedSpendBundleConditions::from(
+                    &allocator,
+                    spend_bundle_conds,
+                )),
+            ),
+            Err(ValidationErr(_, error_code)) => {
+                // a validation error occurred
+                (Some(error_code.into()), None)
+            }
         }
-    }
+    })
 }
 
 #[pyfunction]
 pub fn run_block_generator2<'a>(
-    _py: Python<'a>,
+    py: Python<'a>,
     program: PyBuffer<u8>,
     block_refs: &Bound<'_, PyList>,
     max_cost: Cost,
@@ -68,12 +73,15 @@ pub fn run_block_generator2<'a>(
 ) -> (Option<u32>, Option<OwnedSpendBundleConditions>) {
     let mut allocator = make_allocator(flags);
 
-    let refs = block_refs.into_iter().map(|b| {
-        let buf = b
-            .extract::<PyBuffer<u8>>()
-            .expect("block_refs must be list of buffers");
-        py_to_slice::<'a>(buf)
-    });
+    let refs = block_refs
+        .into_iter()
+        .map(|b| {
+            let buf = b
+                .extract::<PyBuffer<u8>>()
+                .expect("block_refs must be list of buffers");
+            py_to_slice::<'a>(buf)
+        })
+        .collect::<Vec<&'a [u8]>>();
 
     let program = py_to_slice::<'a>(program);
     let run_block = if (flags & ANALYZE_SPENDS) == 0 {
@@ -82,17 +90,19 @@ pub fn run_block_generator2<'a>(
         native_run_block_generator2::<_, MempoolVisitor, _>
     };
 
-    match run_block(&mut allocator, program, refs, max_cost, flags, constants) {
-        Ok(spend_bundle_conds) => (
-            None,
-            Some(OwnedSpendBundleConditions::from(
-                &allocator,
-                spend_bundle_conds,
-            )),
-        ),
-        Err(ValidationErr(_, error_code)) => {
-            // a validation error occurred
-            (Some(error_code.into()), None)
+    py.allow_threads(|| {
+        match run_block(&mut allocator, program, refs, max_cost, flags, constants) {
+            Ok(spend_bundle_conds) => (
+                None,
+                Some(OwnedSpendBundleConditions::from(
+                    &allocator,
+                    spend_bundle_conds,
+                )),
+            ),
+            Err(ValidationErr(_, error_code)) => {
+                // a validation error occurred
+                (Some(error_code.into()), None)
+            }
         }
-    }
+    })
 }