diff --git a/amount.go b/amount.go
index a15b311..e3d6de2 100644
--- a/amount.go
+++ b/amount.go
@@ -360,7 +360,10 @@ func (a Amount) Value() (driver.Value, error) {
 // Allows scanning amounts from a PostgreSQL composite type.
 func (a *Amount) Scan(src interface{}) error {
 	// Wire format: "(9.99,USD)".
-	input := src.(string)
+	input, ok := src.(string)
+	if !ok {
+		return fmt.Errorf("invalid src: %v", src)
+	}
 	if len(input) == 0 {
 		return nil
 	}
diff --git a/amount_test.go b/amount_test.go
index dce7e96..4cdf662 100644
--- a/amount_test.go
+++ b/amount_test.go
@@ -930,3 +930,11 @@ func TestAmount_Scan(t *testing.T) {
 		})
 	}
 }
+
+func TestAmount_ScanNonString(t *testing.T) {
+	var a currency.Amount
+	err := a.Scan(123)
+	if err == nil {
+		t.Errorf("error expected")
+	}
+}