diff --git a/app/javascript/mastodon/components/media_gallery.js b/app/javascript/mastodon/components/media_gallery.js
index a276b17d5..00943e205 100644
--- a/app/javascript/mastodon/components/media_gallery.js
+++ b/app/javascript/mastodon/components/media_gallery.js
@@ -249,7 +249,7 @@ export default class MediaGallery extends React.PureComponent {
       }
 
       children = (
-        <button className='media-spoiler' onClick={this.handleOpen} style={style} ref={this.handleRef}>
+        <button type='button' className='media-spoiler' onClick={this.handleOpen} style={style} ref={this.handleRef}>
           <span className='media-spoiler__warning'>{warning}</span>
           <span className='media-spoiler__trigger'><FormattedMessage id='status.sensitive_toggle' defaultMessage='Click to view' /></span>
         </button>
diff --git a/app/javascript/mastodon/features/video/index.js b/app/javascript/mastodon/features/video/index.js
index 7752fc057..6335d84b6 100644
--- a/app/javascript/mastodon/features/video/index.js
+++ b/app/javascript/mastodon/features/video/index.js
@@ -271,7 +271,7 @@ export default class Video extends React.PureComponent {
           onProgress={this.handleProgress}
         />
 
-        <button className={classNames('video-player__spoiler', { active: !revealed })} onClick={this.toggleReveal}>
+        <button type='button' className={classNames('video-player__spoiler', { active: !revealed })} onClick={this.toggleReveal}>
           <span className='video-player__spoiler__title'><FormattedMessage id='status.sensitive_warning' defaultMessage='Sensitive content' /></span>
           <span className='video-player__spoiler__subtitle'><FormattedMessage id='status.sensitive_toggle' defaultMessage='Click to view' /></span>
         </button>
@@ -290,10 +290,10 @@ export default class Video extends React.PureComponent {
 
           <div className='video-player__buttons-bar'>
             <div className='video-player__buttons left'>
-              <button aria-label={intl.formatMessage(paused ? messages.play : messages.pause)} onClick={this.togglePlay}><i className={classNames('fa fa-fw', { 'fa-play': paused, 'fa-pause': !paused })} /></button>
-              <button aria-label={intl.formatMessage(muted ? messages.unmute : messages.mute)} onClick={this.toggleMute}><i className={classNames('fa fa-fw', { 'fa-volume-off': muted, 'fa-volume-up': !muted })} /></button>
+              <button type='button' aria-label={intl.formatMessage(paused ? messages.play : messages.pause)} onClick={this.togglePlay}><i className={classNames('fa fa-fw', { 'fa-play': paused, 'fa-pause': !paused })} /></button>
+              <button type='button' aria-label={intl.formatMessage(muted ? messages.unmute : messages.mute)} onClick={this.toggleMute}><i className={classNames('fa fa-fw', { 'fa-volume-off': muted, 'fa-volume-up': !muted })} /></button>
 
-              {!onCloseVideo && <button aria-label={intl.formatMessage(messages.hide)} onClick={this.toggleReveal}><i className='fa fa-fw fa-eye' /></button>}
+              {!onCloseVideo && <button type='button' aria-label={intl.formatMessage(messages.hide)} onClick={this.toggleReveal}><i className='fa fa-fw fa-eye' /></button>}
 
               {(detailed || fullscreen) &&
                 <span>
@@ -305,9 +305,9 @@ export default class Video extends React.PureComponent {
             </div>
 
             <div className='video-player__buttons right'>
-              {(!fullscreen && onOpenVideo) && <button aria-label={intl.formatMessage(messages.expand)} onClick={this.handleOpenVideo}><i className='fa fa-fw fa-expand' /></button>}
-              {onCloseVideo && <button aria-label={intl.formatMessage(messages.close)} onClick={this.handleCloseVideo}><i className='fa fa-fw fa-compress' /></button>}
-              <button aria-label={intl.formatMessage(fullscreen ? messages.exit_fullscreen : messages.fullscreen)} onClick={this.toggleFullscreen}><i className={classNames('fa fa-fw', { 'fa-arrows-alt': !fullscreen, 'fa-compress': fullscreen })} /></button>
+              {(!fullscreen && onOpenVideo) && <button type='button' aria-label={intl.formatMessage(messages.expand)} onClick={this.handleOpenVideo}><i className='fa fa-fw fa-expand' /></button>}
+              {onCloseVideo && <button type='button' aria-label={intl.formatMessage(messages.close)} onClick={this.handleCloseVideo}><i className='fa fa-fw fa-compress' /></button>}
+              <button type='button' aria-label={intl.formatMessage(fullscreen ? messages.exit_fullscreen : messages.fullscreen)} onClick={this.toggleFullscreen}><i className={classNames('fa fa-fw', { 'fa-arrows-alt': !fullscreen, 'fa-compress': fullscreen })} /></button>
             </div>
           </div>
         </div>