diff --git a/coding/qr.go b/coding/qr.go
index 4aa5288..bfc3ea4 100644
--- a/coding/qr.go
+++ b/coding/qr.go
@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // Package coding implements low-level QR coding details.
-package coding
+package coding // import "rsc.io/qr/coding"
 
 import (
 	"fmt"
diff --git a/gf256/gf256.go b/gf256/gf256.go
index bfeeeb3..05e5645 100644
--- a/gf256/gf256.go
+++ b/gf256/gf256.go
@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // Package gf256 implements arithmetic over the Galois Field GF(256).
-package gf256
+package gf256 // import "rsc.io/qr/gf256"
 
 import "strconv"
 
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..7fbfc86
--- /dev/null
+++ b/go.mod
@@ -0,0 +1 @@
+module rsc.io/qr
diff --git a/qr.go b/qr.go
index 254b532..ace7e6f 100644
--- a/qr.go
+++ b/qr.go
@@ -5,7 +5,7 @@
 /*
 Package qr encodes QR codes.
 */
-package qr
+package qr // import "rsc.io/qr"
 
 import (
 	"errors"