diff --git a/fontir/src/error.rs b/fontir/src/error.rs
index d55af2a4d..6345ec0e5 100644
--- a/fontir/src/error.rs
+++ b/fontir/src/error.rs
@@ -156,6 +156,8 @@ pub enum WorkError {
     },
     #[error("No source with layerName \"{0}\" exists")]
     NoSourceForName(String),
+    #[error("Source file contained a feature we don't yet support: {0}")]
+    UnsupportedFeature(String),
 }
 
 /// An async work error, hence one that must be Send
diff --git a/fontra2fontir/src/toir.rs b/fontra2fontir/src/toir.rs
index fff96bb80..ec1bf80da 100644
--- a/fontra2fontir/src/toir.rs
+++ b/fontra2fontir/src/toir.rs
@@ -23,13 +23,13 @@ pub(crate) fn to_ir_static_metadata(
         .axes
         .iter()
         .map(|a| match a {
-            crate::fontra::FontraAxis::Discrete(_) => {
-                // Our IR doesn't yet support discrete axes.
-                panic!("Discrete axes are not yet supported: {a:?}")
-            }
-            crate::fontra::FontraAxis::Continuous(a) => a,
+            crate::fontra::FontraAxis::Discrete(_) => Err(WorkError::UnsupportedFeature(format!(
+                "discrete axis {a:?}"
+            ))),
+            crate::fontra::FontraAxis::Continuous(a) => Ok(a),
         })
         .map(|a| {
+            let a = a?;
             let min = UserCoord::new(a.min_value as f32);
             let default = UserCoord::new(a.default_value as f32);
             let max = UserCoord::new(a.max_value as f32);