diff --git a/activitypub.c b/activitypub.c
index 773df78..4d52efa 100644
--- a/activitypub.c
+++ b/activitypub.c
@@ -1476,20 +1476,31 @@ xs_dict *msg_note(snac *snac, const xs_str *content, const xs_val *rcpts,
 
     /* create the attachment list, if there are any */
     if (!xs_is_null(attach)) {
-        int c = 0;
-        while (xs_list_next(attach, &v, &c)) {
-            xs *d            = xs_dict_new();
+        xs_list_foreach(attach, v) {
             const char *url  = xs_list_get(v, 0);
             const char *alt  = xs_list_get(v, 1);
             const char *mime = xs_mime_by_ext(url);
+            int add = 1;
 
-            d = xs_dict_append(d, "mediaType", mime);
-            d = xs_dict_append(d, "url",       url);
-            d = xs_dict_append(d, "name",      alt);
-            d = xs_dict_append(d, "type",
-                xs_startswith(mime, "image/") ? "Image" : "Document");
+            /* check if it's already here */
+            const xs_dict *ad;
+            xs_list_foreach(atls, ad) {
+                if (strcmp(xs_dict_get_def(ad, "url", ""), url) == 0) {
+                    add = 0;
+                    break;
+                }
+            }
 
-            atls = xs_list_append(atls, d);
+            if (add) {
+                xs *d = xs_dict_new();
+                d = xs_dict_append(d, "mediaType", mime);
+                d = xs_dict_append(d, "url",       url);
+                d = xs_dict_append(d, "name",      alt);
+                d = xs_dict_append(d, "type",
+                    xs_startswith(mime, "image/") ? "Image" : "Document");
+
+                atls = xs_list_append(atls, d);
+            }
         }
     }
 
diff --git a/format.c b/format.c
index d0b535d..12783ae 100644
--- a/format.c
+++ b/format.c
@@ -163,14 +163,26 @@ static xs_str *format_line(const char *line, xs_list **attach)
                     const char *mime     = xs_mime_by_ext(img_url);
 
                     if (attach != NULL && xs_startswith(mime, "image/")) {
-                        xs *d = xs_dict_new();
+                        const xs_dict *ad;
+                        int add = 1;
 
-                        d = xs_dict_append(d, "mediaType", mime);
-                        d = xs_dict_append(d, "url",       img_url);
-                        d = xs_dict_append(d, "name",      alt_text);
-                        d = xs_dict_append(d, "type",      "Image");
+                        xs_list_foreach(*attach, ad) {
+                            if (strcmp(xs_dict_get_def(ad, "url", ""), img_url) == 0) {
+                                add = 0;
+                                break;
+                            }
+                        }
 
-                        *attach = xs_list_append(*attach, d);
+                        if (add) {
+                            xs *d = xs_dict_new();
+
+                            d = xs_dict_append(d, "mediaType", mime);
+                            d = xs_dict_append(d, "url",       img_url);
+                            d = xs_dict_append(d, "name",      alt_text);
+                            d = xs_dict_append(d, "type",      "Image");
+
+                            *attach = xs_list_append(*attach, d);
+                        }
                     }
                     else {
                         xs *link = xs_fmt("<a href=\"%s\">%s</a>", img_url, alt_text);
@@ -191,14 +203,26 @@ static xs_str *format_line(const char *line, xs_list **attach)
 
                 if (attach != NULL && xs_startswith(mime, "image/")) {
                     /* if it's a link to an image, insert it as an attachment */
-                    xs *d = xs_dict_new();
+                    const xs_dict *ad;
+                    int add = 1;
 
-                    d = xs_dict_append(d, "mediaType", mime);
-                    d = xs_dict_append(d, "url",       v2);
-                    d = xs_dict_append(d, "name",      "");
-                    d = xs_dict_append(d, "type",      "Image");
+                    xs_list_foreach(*attach, ad) {
+                        if (strcmp(xs_dict_get_def(ad, "url", ""), v2) == 0) {
+                            add = 0;
+                            break;
+                        }
+                    }
 
-                    *attach = xs_list_append(*attach, d);
+                    if (add) {
+                        xs *d = xs_dict_new();
+
+                        d = xs_dict_append(d, "mediaType", mime);
+                        d = xs_dict_append(d, "url",       v2);
+                        d = xs_dict_append(d, "name",      "");
+                        d = xs_dict_append(d, "type",      "Image");
+
+                        *attach = xs_list_append(*attach, d);
+                    }
                 }
                 else {
                     xs *s1 = xs_fmt("<a href=\"%s\" target=\"_blank\">%s</a>", v2, u);