diff --git a/internal/sqlite3test/raw.go b/internal/sqlite3test/raw.go
new file mode 100644
index 0000000..aed2e69
--- /dev/null
+++ b/internal/sqlite3test/raw.go
@@ -0,0 +1,35 @@
+package sqlite3test
+
+/*
+#cgo CFLAGS: -DUSE_LIBSQLITE3
+#cgo linux LDFLAGS: -lsqlite3
+#cgo darwin LDFLAGS: -L/usr/local/opt/sqlite/lib -lsqlite3
+#cgo darwin CFLAGS: -I/usr/local/opt/sqlite/include
+#cgo openbsd LDFLAGS: -lsqlite3
+#cgo solaris LDFLAGS: -lsqlite3
+#include <stdlib.h>
+#include <sqlite3.h>
+
+static void one(sqlite3_context* ctx, int n, sqlite3_value** vals) {
+    sqlite3_result_int(ctx, 1);
+}
+
+static inline int _create_function(sqlite3* c) {
+    return sqlite3_create_function(c, "one", 0, SQLITE_UTF8|SQLITE_DETERMINISTIC, NULL, one, NULL, NULL);
+}
+*/
+import "C"
+import (
+	sqlite3 "github.com/mattn/go-sqlite3"
+	"unsafe"
+)
+
+func RegisterFunction(conn *sqlite3.SQLiteConn) error {
+	return conn.Raw(func(raw unsafe.Pointer) error {
+		rawConn := (*C.sqlite3)(raw)
+		if ret := C._create_function(rawConn); ret != C.SQLITE_OK {
+			return sqlite3.ErrNo(ret)
+		}
+		return nil
+	})
+}
diff --git a/raw_test.go b/raw_test.go
new file mode 100644
index 0000000..9ac4cbf
--- /dev/null
+++ b/raw_test.go
@@ -0,0 +1,37 @@
+package sqlite3_test
+
+import (
+	"database/sql"
+	"testing"
+
+	sqlite3 "github.com/mattn/go-sqlite3"
+	"github.com/mattn/go-sqlite3/internal/sqlite3test"
+)
+
+func TestRaw(t *testing.T) {
+	sql.Register("sqlite3_rawtest", &sqlite3.SQLiteDriver{
+		ConnectHook: func(c *sqlite3.SQLiteConn) error {
+			return sqlite3test.RegisterFunction(c)
+		},
+	})
+
+	db, err := sql.Open("sqlite3_rawtest", "...")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer db.Close()
+
+	if err := db.Ping(); err != nil {
+		t.Fatal(err)
+	}
+
+	var result int
+	if err := db.QueryRow(`SELECT one()`).Scan(&result); err != nil {
+		t.Fatal(err)
+	}
+
+	if result != 1 {
+		t.Errorf("expected custom one() function to return 1, but got %d", result)
+	}
+}