diff --git a/hugr-core/src/builder/dataflow.rs b/hugr-core/src/builder/dataflow.rs
index c81d684d2..736cc7659 100644
--- a/hugr-core/src/builder/dataflow.rs
+++ b/hugr-core/src/builder/dataflow.rs
@@ -138,7 +138,11 @@ impl FunctionBuilder<Hugr> {
     /// # Errors
     ///
     /// Error in adding DFG child nodes.
-    pub fn new(name: impl Into<String>, signature: PolyFuncType) -> Result<Self, BuildError> {
+    pub fn new(
+        name: impl Into<String>,
+        signature: impl Into<PolyFuncType>,
+    ) -> Result<Self, BuildError> {
+        let signature = signature.into();
         let body = signature.body().clone();
         let op = ops::FuncDefn {
             signature,
@@ -328,10 +332,8 @@ pub(crate) mod test {
     #[test]
     fn simple_inter_graph_edge() {
         let builder = || -> Result<Hugr, BuildError> {
-            let mut f_build = FunctionBuilder::new(
-                "main",
-                FunctionType::new(type_row![BIT], type_row![BIT]).into(),
-            )?;
+            let mut f_build =
+                FunctionBuilder::new("main", FunctionType::new(type_row![BIT], type_row![BIT]))?;
 
             let [i1] = f_build.input_wires_arr();
             let noop = f_build.add_dataflow_op(Noop { ty: BIT }, [i1])?;
@@ -352,10 +354,8 @@ pub(crate) mod test {
 
     #[test]
     fn error_on_linear_inter_graph_edge() -> Result<(), BuildError> {
-        let mut f_build = FunctionBuilder::new(
-            "main",
-            FunctionType::new(type_row![QB], type_row![QB]).into(),
-        )?;
+        let mut f_build =
+            FunctionBuilder::new("main", FunctionType::new(type_row![QB], type_row![QB]))?;
 
         let [i1] = f_build.input_wires_arr();
         let noop = f_build.add_dataflow_op(Noop { ty: QB }, [i1])?;
diff --git a/hugr-core/src/hugr/views/sibling_subgraph.rs b/hugr-core/src/hugr/views/sibling_subgraph.rs
index 24e03c368..889e5e5ae 100644
--- a/hugr-core/src/hugr/views/sibling_subgraph.rs
+++ b/hugr-core/src/hugr/views/sibling_subgraph.rs
@@ -415,7 +415,7 @@ impl SiblingSubgraph {
     /// The new Hugr will contain a [FuncDefn][crate::ops::FuncDefn] root
     /// with the same signature as the subgraph and the specified `name`
     pub fn extract_subgraph(&self, hugr: &impl HugrView, name: impl Into<String>) -> Hugr {
-        let mut builder = FunctionBuilder::new(name, self.signature(hugr).into()).unwrap();
+        let mut builder = FunctionBuilder::new(name, self.signature(hugr)).unwrap();
         // Take the unfinished Hugr from the builder, to avoid unnecessary
         // validation checks that require connecting the inputs and outputs.
         let mut extracted = mem::take(builder.hugr_mut());