diff --git a/crates/wit-component/src/encoding.rs b/crates/wit-component/src/encoding.rs
index f0992100fd..5e5fa09953 100644
--- a/crates/wit-component/src/encoding.rs
+++ b/crates/wit-component/src/encoding.rs
@@ -515,7 +515,11 @@ impl<'a> EncodingState<'a> {
             .exported_instances
             .get(&interface)
             .copied()
-            .unwrap_or_else(|| self.imported_instances[&interface]);
+            .unwrap_or_else(|| {
+                *self.imported_instances.get(&interface).unwrap_or_else(|| {
+                    panic!("interface with index {} of type with index {} missing from imported instances", interface.index(), id.index())
+                })
+            });
         self.component.alias_type_export(instance, name)
     }
 
diff --git a/crates/wit-component/src/metadata.rs b/crates/wit-component/src/metadata.rs
index 005e518f34..ad58e477a7 100644
--- a/crates/wit-component/src/metadata.rs
+++ b/crates/wit-component/src/metadata.rs
@@ -163,7 +163,14 @@ pub fn encode(
             .iter()
             .filter(|(_, p)| p.name == pkg.name)
             .count()
-            == 1
+            == 1,
+        "expected exactly one package with name {}, got names: {:?}",
+        pkg.name,
+        resolve
+            .packages
+            .iter()
+            .map(|(_x, p)| p.name.clone())
+            .collect::<Vec<_>>()
     );
 
     let mut ret = Vec::new();