diff --git a/crates/tor-error/src/lib.rs b/crates/tor-error/src/lib.rs
index dfe936064..b12daf851 100644
--- a/crates/tor-error/src/lib.rs
+++ b/crates/tor-error/src/lib.rs
@@ -159,16 +159,33 @@ pub enum ErrorKind {
 
     /// A requested operation was not implemented by Arti.
     ///
-    /// This kind of error can happen when calling an API that isn't available
-    /// at runtime, or when requesting a piece of protocol functionality that is
-    /// not implemented.
+    /// This kind of error can happen when requesting a piece of protocol
+    /// functionality that has not (yet) been implemented in the Arti project.
     ///
     /// If it happens as a result of a user activity, it's fine to ignore, log,
     /// or report the error. If it happens as a result of direct API usage, it
-    /// may indicate that you're using something that isn't implemented yet, or
-    /// hasn't been turned on for your build environment.
-    #[display(fmt = "operation not supported")]
-    NoSupport,
+    /// may indicate that you're using something that isn't implemented yet.
+    ///
+    /// This kind can relate both to operations which we plan to implement, and
+    /// to operations which we do not.  It does not relate to faciities which
+    /// are disabled (e.g. at build time) or harmful.
+    ///
+    /// It can refer to facilities which were once implemented in Tor or Arti
+    /// but for which support has been removed.
+    #[display(fmt = "operation not implemented")]
+    NotImplemented,
+
+    /// A feature was requested which has been disabled in this build of Arti.
+    ///!
+    /// This kind of error happens when the running Arti was built wityout the
+    /// appropriate feature (usually, cargo feature) enabled.
+    ///!
+    /// This might indicate that the overall running system has been
+    /// mis-configured at build-time.  Alternatively, it can occur if the
+    /// running system is deliberately stripped down, in which case it might be
+    /// reasonable to simply report this error to a user.
+    #[display(fmt = "operation not supported because Arti feature disabled")]
+    FeatureDisabled,
 
     /// Someone or something violated a network protocol.
     ///
diff --git a/crates/tor-socksproto/src/err.rs b/crates/tor-socksproto/src/err.rs
index 0733cf50e..c5d9ad252 100644
--- a/crates/tor-socksproto/src/err.rs
+++ b/crates/tor-socksproto/src/err.rs
@@ -31,8 +31,8 @@ pub enum Error {
 
     /// The SOCKS client tried to use a SOCKS feature that we don't
     /// support at all.
-    #[error("SOCKS feature not supported")]
-    NoSupport,
+    #[error("SOCKS feature not implemented")]
+    NotImplemented,
 
     /// Tried to progress the SOCKS handshake when it was already
     /// finished.  This is a programming error.
@@ -59,7 +59,7 @@ impl HasKind for Error {
             }
             E::Syntax | E::Decode(_) | E::BadProtocol(_) => EK::ProtocolViolation,
             E::Invalid(_) => EK::BadArgument,
-            E::NoSupport => EK::NoSupport,
+            E::NotImplemented => EK::NotImplemented,
             E::AlreadyFinished(_) => EK::Internal,
             E::Internal(_) => EK::Internal,
         }
diff --git a/crates/tor-socksproto/src/handshake.rs b/crates/tor-socksproto/src/handshake.rs
index 742c25e86..14f51cb28 100644
--- a/crates/tor-socksproto/src/handshake.rs
+++ b/crates/tor-socksproto/src/handshake.rs
@@ -180,7 +180,7 @@ impl SocksHandshake {
             (State::Socks5Wait, [5, NO_AUTHENTICATION])
         } else {
             // In theory we should reply with "NO ACCEPTABLE METHODS".
-            return Err(Error::NoSupport);
+            return Err(Error::NotImplemented);
         };
 
         self.state = next;
@@ -197,7 +197,7 @@ impl SocksHandshake {
 
         let ver = r.take_u8()?;
         if ver != 1 {
-            return Err(Error::NoSupport);
+            return Err(Error::NotImplemented);
         }
 
         let ulen = r.take_u8()?;
@@ -445,7 +445,7 @@ mod test {
     fn socks5_init_nothing_works() {
         let mut h = SocksHandshake::new();
         let a = h.handshake(&hex!("05 02 9988")[..]);
-        assert!(matches!(a, Ok(Err(Error::NoSupport))));
+        assert!(matches!(a, Ok(Err(Error::NotImplemented))));
     }
 
     #[test]
diff --git a/crates/tor-socksproto/src/msg.rs b/crates/tor-socksproto/src/msg.rs
index be67008d3..a97d3d7c7 100644
--- a/crates/tor-socksproto/src/msg.rs
+++ b/crates/tor-socksproto/src/msg.rs
@@ -200,7 +200,7 @@ impl SocksRequest {
         auth: SocksAuth,
     ) -> Result<Self> {
         if !cmd.recognized() {
-            return Err(Error::NoSupport);
+            return Err(Error::NotImplemented);
         }
         if port == 0 && cmd.requires_port() {
             return Err(Error::Syntax);
@@ -298,7 +298,7 @@ mod test {
             1024,
             SocksAuth::NoAuth,
         );
-        assert!(matches!(e, Err(Error::NoSupport)));
+        assert!(matches!(e, Err(Error::NotImplemented)));
 
         let e = SocksRequest::new(
             SocksVersion::V4,