diff --git a/src/transform/common.rs b/src/transform/common.rs
index e39d149..71a325d 100644
--- a/src/transform/common.rs
+++ b/src/transform/common.rs
@@ -83,14 +83,18 @@ impl Default for CheckLevel {
 }
 
 pub(crate) fn check_mergeable_fieldsets(
+    a_name: &str,
     a: &FieldSet,
+    b_name: &str,
     b: &FieldSet,
     level: CheckLevel,
 ) -> anyhow::Result<()> {
     if let Err(e) = check_mergeable_fieldsets_inner(a, b, level) {
         bail!(
-            "Cannot merge fieldsets.\nfirst: {:#?}\nsecond: {:#?}\ncause: {:?}",
+            "Cannot merge fieldsets.\nfirst: {} {:#?}\nsecond: {} {:#?}\ncause: {:?}",
+            a_name,
             a,
+            b_name,
             b,
             e
         )
diff --git a/src/transform/merge_fieldsets.rs b/src/transform/merge_fieldsets.rs
index 6e1cbfa..380f420 100644
--- a/src/transform/merge_fieldsets.rs
+++ b/src/transform/merge_fieldsets.rs
@@ -51,7 +51,7 @@ impl MergeFieldsets {
 
         for id in &ids {
             let fs2 = ir.fieldsets.get(id).unwrap();
-            check_mergeable_fieldsets(&fs, fs2, self.check)?;
+            check_mergeable_fieldsets(&main_id, &fs, id, fs2, self.check)?;
         }
 
         for id in &ids {