1 files changed, 8 insertions, 0 deletions
diff --git a/sw/cal/err.go b/sw/cal/err.go
index 452e5f0..26ef5df 100644
--- a/sw/cal/err.go
+++ b/sw/cal/err.go
@@ -32,3 +32,11 @@ type ErrNoSig struct {
 func (e ErrNoSig) Error() string {
 	return fmt.Sprintf("%s: no such signal '%s'", e.filename, e.signal)
 }
+
+type ErrDupKey struct {
+	key int32
+}
+
+func (e ErrDupKey) Error() string {
+	return fmt.Sprintf("duplicate key %d", e.key)
+}