diff --git a/app/javascript/flavours/glitch/actions/compose.js b/app/javascript/flavours/glitch/actions/compose.js
index 7a4af4cda7..267cff563c 100644
--- a/app/javascript/flavours/glitch/actions/compose.js
+++ b/app/javascript/flavours/glitch/actions/compose.js
@@ -181,6 +181,18 @@ export function submitCompose(routerHistory) {
 
     dispatch(submitComposeRequest());
 
+    // If we're editing a post with media attachments, those have not
+    // necessarily been changed on the server. Do it now in the same
+    // API call.
+    let media_attributes;
+    if (statusId !== null) {
+      media_attributes = media.map(item => ({
+        id: item.get('id'),
+        description: item.get('description'),
+        focus: item.get('focus'),
+      }));
+    }
+
     api(getState).request({
       url: statusId === null ? '/api/v1/statuses' : `/api/v1/statuses/${statusId}`,
       method: statusId === null ? 'post' : 'put',
@@ -189,6 +201,7 @@ export function submitCompose(routerHistory) {
         content_type: getState().getIn(['compose', 'content_type']),
         in_reply_to_id: getState().getIn(['compose', 'in_reply_to'], null),
         media_ids: media.map(item => item.get('id')),
+        media_attributes,
         sensitive: getState().getIn(['compose', 'sensitive']) || (spoilerText.length > 0 && media.size !== 0),
         spoiler_text: spoilerText,
         visibility: getState().getIn(['compose', 'privacy']),
@@ -415,11 +428,31 @@ export function changeUploadCompose(id, params) {
   return (dispatch, getState) => {
     dispatch(changeUploadComposeRequest());
 
-    api(getState).put(`/api/v1/media/${id}`, params).then(response => {
-      dispatch(changeUploadComposeSuccess(response.data));
-    }).catch(error => {
-      dispatch(changeUploadComposeFail(id, error));
-    });
+    let media = getState().getIn(['compose', 'media_attachments']).find((item) => item.get('id') === id);
+
+    // Editing already-attached media is deferred to editing the post itself.
+    // For simplicity's sake, fake an API reply.
+    if (media && !media.get('unattached')) {
+      let { description, focus } = params;
+      const data = media.toJS();
+
+      if (description) {
+        data.description = description;
+      }
+
+      if (focus) {
+        focus = focus.split(',');
+        data.meta = { focus: { x: parseFloat(focus[0]), y: parseFloat(focus[1]) } };
+      }
+
+      dispatch(changeUploadComposeSuccess(data, true));
+    } else {
+      api(getState).put(`/api/v1/media/${id}`, params).then(response => {
+        dispatch(changeUploadComposeSuccess(response.data, false));
+      }).catch(error => {
+        dispatch(changeUploadComposeFail(id, error));
+      });
+    }
   };
 };
 
@@ -430,10 +463,11 @@ export function changeUploadComposeRequest() {
   };
 };
 
-export function changeUploadComposeSuccess(media) {
+export function changeUploadComposeSuccess(media, attached) {
   return {
     type: COMPOSE_UPLOAD_CHANGE_SUCCESS,
     media: media,
+    attached: attached,
     skipLoading: true,
   };
 };
diff --git a/app/javascript/flavours/glitch/features/compose/components/upload.js b/app/javascript/flavours/glitch/features/compose/components/upload.js
index 6528bbc84c..cd45245409 100644
--- a/app/javascript/flavours/glitch/features/compose/components/upload.js
+++ b/app/javascript/flavours/glitch/features/compose/components/upload.js
@@ -43,13 +43,13 @@ export default class Upload extends ImmutablePureComponent {
           {({ scale }) => (
             <div className='compose-form__upload-thumbnail' style={{ transform: `scale(${scale})`, backgroundImage: `url(${media.get('preview_url')})`, backgroundPosition: `${x}% ${y}%` }}>
               <div className='compose-form__upload__actions'>
-                <button className='icon-button' onClick={this.handleUndoClick}><Icon id='times' /> <FormattedMessage id='upload_form.undo' defaultMessage='Delete' /></button>
-                {!!media.get('unattached') && (<button className='icon-button' onClick={this.handleFocalPointClick}><Icon id='pencil' /> <FormattedMessage id='upload_form.edit' defaultMessage='Edit' /></button>)}
+                <button type='button' className='icon-button' onClick={this.handleUndoClick}><Icon id='times' /> <FormattedMessage id='upload_form.undo' defaultMessage='Delete' /></button>
+                <button type='button' className='icon-button' onClick={this.handleFocalPointClick}><Icon id='pencil' /> <FormattedMessage id='upload_form.edit' defaultMessage='Edit' /></button>
               </div>
 
-              {(media.get('description') || '').length === 0 && !!media.get('unattached') && (
+              {(media.get('description') || '').length === 0 && (
                 <div className='compose-form__upload__warning'>
-                  <button className='icon-button' onClick={this.handleFocalPointClick}><Icon id='info-circle' /> <FormattedMessage id='upload_form.description_missing' defaultMessage='No description added' /></button>
+                  <button type='button' className='icon-button' onClick={this.handleFocalPointClick}><Icon id='info-circle' /> <FormattedMessage id='upload_form.description_missing' defaultMessage='No description added' /></button>
                 </div>
               )}
             </div>
diff --git a/app/javascript/flavours/glitch/features/ui/components/focal_point_modal.js b/app/javascript/flavours/glitch/features/ui/components/focal_point_modal.js
index 0dd07fb76b..fb432cf9ca 100644
--- a/app/javascript/flavours/glitch/features/ui/components/focal_point_modal.js
+++ b/app/javascript/flavours/glitch/features/ui/components/focal_point_modal.js
@@ -320,7 +320,7 @@ class FocalPointModal extends ImmutablePureComponent {
               <React.Fragment>
                 <label className='setting-text-label' htmlFor='upload-modal__thumbnail'><FormattedMessage id='upload_form.thumbnail' defaultMessage='Change thumbnail' /></label>
 
-                <Button disabled={isUploadingThumbnail} text={intl.formatMessage(messages.chooseImage)} onClick={this.handleFileInputClick} />
+                <Button disabled={isUploadingThumbnail || !media.get('unattached')} text={intl.formatMessage(messages.chooseImage)} onClick={this.handleFileInputClick} />
 
                 <label>
                   <span style={{ display: 'none' }}>{intl.formatMessage(messages.chooseImage)}</span>
diff --git a/app/javascript/flavours/glitch/reducers/compose.js b/app/javascript/flavours/glitch/reducers/compose.js
index 814b6a1a72..a69c0f7f2d 100644
--- a/app/javascript/flavours/glitch/reducers/compose.js
+++ b/app/javascript/flavours/glitch/reducers/compose.js
@@ -551,7 +551,7 @@ export default function compose(state = initialState, action) {
       .setIn(['media_modal', 'dirty'], false)
       .update('media_attachments', list => list.map(item => {
         if (item.get('id') === action.media.id) {
-          return fromJS(action.media).set('unattached', true);
+          return fromJS(action.media).set('unattached', !action.attached);
         }
 
         return item;