1 files changed, 11 insertions, 0 deletions
diff --git a/err.go b/err.go
new file mode 100644
index 0000000..48c8b12
--- /dev/null
+++ b/err.go
@@ -0,0 +1,11 @@
+package exchange
+
+import "fmt"
+
+type errBadCurrency struct {
+	symbol string
+}
+
+func (e errBadCurrency) Error() string {
+	return fmt.Sprintf("unknown currency symbol %q", e.symbol)
+}