diff --git a/src/cmd/aquila/add.zig b/src/cmd/aquila/add.zig
index e57b791e6bdc9e32eab9a114e673cdd469630010..b9467c817414abefed55db3a81b988690c137791 100644
--- a/src/cmd/aquila/add.zig
+++ b/src/cmd/aquila/add.zig
@@ -9,18 +9,32 @@ const aq = @import("./../aq.zig");
 
 pub fn execute(args: [][]u8) !void {
     const pkg_id = args[0];
+    _ = try do(std.fs.cwd(), pkg_id);
+    std.log.info("Successfully added package {s}", .{pkg_id});
+}
 
+pub fn do(dir: std.fs.Dir, pkg_id: []const u8) ![]const u8 {
     const url = try std.mem.join(gpa, "/", &.{ aq.server_root, pkg_id });
     const val = try aq.server_fetch(url);
 
-    const file = try std.fs.cwd().openFile("zig.mod", .{ .read = true, .write = true });
-    try file.seekTo(try file.getEndPos());
-
-    const file_w = file.writer();
-    try file_w.print("  - src: git https://{s}/{s}\n", .{
+    const pkg_url = try std.fmt.allocPrint(gpa, "https://{s}/{s}", .{
         val.get(.{ "repo", "domain" }).?.String,
         val.get(.{ "pkg", "remote_name" }).?.String,
     });
 
-    std.log.info("Successfully added package {s}", .{pkg_id});
+    const m = try u.ModFile.from_dir(gpa, dir);
+    for (m.devdeps) |d| {
+        if (std.mem.eql(u8, d.path, pkg_url)) {
+            return pkg_url;
+        }
+    }
+
+    const file = try dir.openFile("zig.mod", .{ .read = true, .write = true });
+    defer file.close();
+    try file.seekTo(try file.getEndPos());
+
+    const file_w = file.writer();
+    try file_w.print("  - src: git {s}\n", .{pkg_url});
+
+    return pkg_url;
 }