diff --git a/crates/macros/src/lib.rs b/crates/macros/src/lib.rs
index a66ad3aa..991671e8 100644
--- a/crates/macros/src/lib.rs
+++ b/crates/macros/src/lib.rs
@@ -163,19 +163,21 @@ pub fn connect(attr: proc_macro::TokenStream) -> proc_macro::TokenStream {
 
     out.extend(quote! {
         use futuresdr::runtime::Block;
+        use futuresdr::runtime::Error;
         use futuresdr::runtime::Flowgraph;
+        use std::result::Result;
 
         struct FgOp;
         trait Add<T> {
-            fn add(fg: &mut Flowgraph, b: T) -> Result<usize>;
+            fn add(fg: &mut Flowgraph, b: T) -> Result<usize, Error>;
         }
         impl Add<usize> for FgOp {
-            fn add(_fg: &mut Flowgraph, b: usize) -> Result<usize> {
+            fn add(_fg: &mut Flowgraph, b: usize) -> Result<usize, Error> {
                 Ok(b)
             }
         }
         impl Add<Block> for FgOp {
-            fn add(fg: &mut Flowgraph, b: Block) -> Result<usize> {
+            fn add(fg: &mut Flowgraph, b: Block) -> Result<usize, Error> {
                 fg.add_block(b)
             }
         }
diff --git a/src/runtime/flowgraph.rs b/src/runtime/flowgraph.rs
index d1a383c7..4bbe469d 100644
--- a/src/runtime/flowgraph.rs
+++ b/src/runtime/flowgraph.rs
@@ -4,9 +4,7 @@ use futures::SinkExt;
 use std::cmp::PartialEq;
 use std::fmt::Debug;
 use std::hash::Hash;
-use std::result;
 
-use crate::anyhow::Result;
 #[cfg(not(target_arch = "wasm32"))]
 use crate::runtime::buffer::circular::Circular;
 #[cfg(target_arch = "wasm32")]
@@ -41,8 +39,8 @@ impl Flowgraph {
     }
 
     /// Add [`Block`] to flowgraph
-    pub fn add_block(&mut self, block: Block) -> Result<usize> {
-        Ok(self.topology.as_mut().unwrap().add_block(block)?)
+    pub fn add_block(&mut self, block: Block) -> Result<usize, Error> {
+        self.topology.as_mut().unwrap().add_block(block)
     }
 
     /// Make stream connection
@@ -148,8 +146,8 @@ impl FlowgraphHandle {
         block_id: usize,
         port_id: impl Into<PortId>,
         data: Pmt,
-    ) -> result::Result<(), Error> {
-        let (tx, rx) = oneshot::channel::<result::Result<(), Error>>();
+    ) -> Result<(), Error> {
+        let (tx, rx) = oneshot::channel::<Result<(), Error>>();
         self.inbox
             .send(FlowgraphMessage::BlockCall {
                 block_id,
@@ -168,8 +166,8 @@ impl FlowgraphHandle {
         block_id: usize,
         port_id: impl Into<PortId>,
         data: Pmt,
-    ) -> result::Result<Pmt, Error> {
-        let (tx, rx) = oneshot::channel::<result::Result<Pmt, Error>>();
+    ) -> Result<Pmt, Error> {
+        let (tx, rx) = oneshot::channel::<Result<Pmt, Error>>();
         self.inbox
             .send(FlowgraphMessage::BlockCallback {
                 block_id,
@@ -183,7 +181,7 @@ impl FlowgraphHandle {
     }
 
     /// Get [`FlowgraphDescription`]
-    pub async fn description(&mut self) -> result::Result<FlowgraphDescription, Error> {
+    pub async fn description(&mut self) -> Result<FlowgraphDescription, Error> {
         let (tx, rx) = oneshot::channel::<FlowgraphDescription>();
         self.inbox
             .send(FlowgraphMessage::FlowgraphDescription { tx })
@@ -194,28 +192,34 @@ impl FlowgraphHandle {
     }
 
     /// Get [`BlockDescription`]
-    pub async fn block_description(&mut self, block_id: usize) -> Result<BlockDescription> {
-        let (tx, rx) = oneshot::channel::<result::Result<BlockDescription, Error>>();
+    pub async fn block_description(&mut self, block_id: usize) -> Result<BlockDescription, Error> {
+        let (tx, rx) = oneshot::channel::<Result<BlockDescription, Error>>();
         self.inbox
             .send(FlowgraphMessage::BlockDescription { block_id, tx })
-            .await?;
-        let d = rx.await??;
+            .await
+            .map_err(|_| Error::InvalidBlock(block_id))?;
+        let d = rx.await.map_err(|_| Error::InvalidBlock(block_id))??;
         Ok(d)
     }
 
     /// Send a terminate message to the [`Flowgraph`]
     ///
     /// Does not wait until the [`Flowgraph`] is actually terminated.
-    pub async fn terminate(&mut self) -> Result<()> {
-        self.inbox.send(FlowgraphMessage::Terminate).await?;
+    pub async fn terminate(&mut self) -> Result<(), Error> {
+        self.inbox
+            .send(FlowgraphMessage::Terminate)
+            .await
+            .map_err(|_| Error::FlowgraphTerminated)?;
         Ok(())
     }
 
     /// Terminate the [`Flowgraph`]
     ///
     /// Send a terminate message to the [`Flowgraph`] and wait until it is shutdown.
-    pub async fn terminate_and_wait(&mut self) -> Result<()> {
-        self.terminate().await?;
+    pub async fn terminate_and_wait(&mut self) -> Result<(), Error> {
+        self.terminate()
+            .await
+            .map_err(|_| Error::FlowgraphTerminated)?;
         while !self.inbox.is_closed() {
             #[cfg(not(target_arch = "wasm32"))]
             async_io::Timer::after(std::time::Duration::from_millis(200)).await;
diff --git a/src/runtime/topology.rs b/src/runtime/topology.rs
index 01204f79..8877be5a 100644
--- a/src/runtime/topology.rs
+++ b/src/runtime/topology.rs
@@ -118,7 +118,7 @@ impl Topology {
     }
 
     /// Adds a [Block] to the [Topology] returning the `id` of the [Block] in the [Topology].
-    pub fn add_block(&mut self, mut block: Block) -> Result<usize, crate::runtime::Error> {
+    pub fn add_block(&mut self, mut block: Block) -> Result<usize, Error> {
         if let Some(name) = block.instance_name() {
             if self.block_id(name).is_some() {
                 return Err(Error::DuplicateBlockName(name.to_string()));