diff --git a/public_html/templates/post.tpl b/public_html/templates/post.tpl
index cfa933dd..b2d7a255 100644
--- a/public_html/templates/post.tpl
+++ b/public_html/templates/post.tpl
@@ -11,7 +11,7 @@
 <% } else if (post.contentType == 'flash') { %>
 
 	<object
-			type="application/x-shockwave-flash"
+			type="<%= post.contentMimeType %>"
 			width="<%= post.imageWidth %>"
 			height="<%= post.imageHeight %>"
 			data="<%= postContentUrl %>">
@@ -22,7 +22,7 @@
 <% } else if (post.contentType == 'video') { %>
 
 	<video controls>
-		<source src="<%= postContentUrl %>"/>
+		<source type="<%= post.contentMimeType %>" src="<%= postContentUrl %>"/>
 
 		Your browser doesn't support HTML5 videos.
 	</video>
diff --git a/src/Controllers/ViewProxies/PostViewProxy.php b/src/Controllers/ViewProxies/PostViewProxy.php
index 237f4bbc..b2c63108 100644
--- a/src/Controllers/ViewProxies/PostViewProxy.php
+++ b/src/Controllers/ViewProxies/PostViewProxy.php
@@ -16,6 +16,7 @@ class PostViewProxy extends AbstractViewProxy
 			$result->safety = \Szurubooru\Helpers\EnumHelper::postSafetyToString($post->getSafety());
 			$result->contentType = \Szurubooru\Helpers\EnumHelper::postTypeToString($post->getContentType());
 			$result->contentChecksum = $post->getContentChecksum();
+			$result->contentMimeType = $post->getContentMimeType();
 			$result->source = $post->getSource();
 			$result->imageWidth = $post->getImageWidth();
 			$result->imageHeight = $post->getImageHeight();
diff --git a/src/Dao/EntityConverters/PostEntityConverter.php b/src/Dao/EntityConverters/PostEntityConverter.php
index 4feebfde..07133907 100644
--- a/src/Dao/EntityConverters/PostEntityConverter.php
+++ b/src/Dao/EntityConverters/PostEntityConverter.php
@@ -15,6 +15,7 @@ class PostEntityConverter extends AbstractEntityConverter implements IEntityConv
 			'safety' => $entity->getSafety(),
 			'contentType' => $entity->getContentType(),
 			'contentChecksum' => $entity->getContentChecksum(),
+			'contentMimeType' => $entity->getContentMimeType(),
 			'source' => $entity->getSource(),
 			'imageWidth' => $entity->getImageWidth(),
 			'imageHeight' => $entity->getImageHeight(),
@@ -33,6 +34,7 @@ class PostEntityConverter extends AbstractEntityConverter implements IEntityConv
 		$entity->setSafety(intval($array['safety']));
 		$entity->setContentType(intval($array['contentType']));
 		$entity->setContentChecksum($array['contentChecksum']);
+		$entity->setContentMimeType($array['contentMimeType']);
 		$entity->setSource($array['source']);
 		$entity->setImageWidth($array['imageWidth']);
 		$entity->setImageHeight($array['imageHeight']);
diff --git a/src/Entities/Post.php b/src/Entities/Post.php
index eda44e71..3e1f8bf5 100644
--- a/src/Entities/Post.php
+++ b/src/Entities/Post.php
@@ -19,6 +19,7 @@ final class Post extends Entity
 	protected $safety;
 	protected $contentType;
 	protected $contentChecksum;
+	protected $contentMimeType;
 	protected $source;
 	protected $imageWidth;
 	protected $imageHeight;
@@ -112,6 +113,16 @@ final class Post extends Entity
 		$this->contentChecksum = $contentChecksum;
 	}
 
+	public function getContentMimeType()
+	{
+		return $this->contentMimeType;
+	}
+
+	public function setContentMimeType($contentMimeType)
+	{
+		$this->contentMimeType = $contentMimeType;
+	}
+
 	public function getSource()
 	{
 		return $this->source;
diff --git a/src/Services/PostService.php b/src/Services/PostService.php
index 03f0d436..b070a2b9 100644
--- a/src/Services/PostService.php
+++ b/src/Services/PostService.php
@@ -131,6 +131,7 @@ class PostService
 			throw new \DomainException('Upload is too big.');
 
 		$mime = \Szurubooru\Helpers\MimeHelper::getMimeTypeFromBuffer($content);
+		$post->setContentMimeType($mime);
 
 		if (\Szurubooru\Helpers\MimeHelper::isFlash($mime))
 			$post->setContentType(\Szurubooru\Entities\Post::POST_TYPE_FLASH);
diff --git a/src/Upgrades/Upgrade04.php b/src/Upgrades/Upgrade04.php
new file mode 100644
index 00000000..80c36357
--- /dev/null
+++ b/src/Upgrades/Upgrade04.php
@@ -0,0 +1,34 @@
+<?php
+namespace Szurubooru\Upgrades;
+
+class Upgrade04 implements IUpgrade
+{
+	private $postService;
+	private $fileService;
+
+	public function __construct(
+		\Szurubooru\Services\PostService $postService,
+		\Szurubooru\Services\FileService $fileService)
+	{
+		$this->postService = $postService;
+		$this->fileService = $fileService;
+	}
+
+	public function run(\Szurubooru\DatabaseConnection $databaseConnection)
+	{
+		$databaseConnection->getPDO()->exec('ALTER TABLE "posts" ADD COLUMN contentMimeType TEXT DEFAULT NULL');
+
+		$postDao = new \Szurubooru\Dao\PostDao($databaseConnection);
+		$posts = $postDao->findAll();
+		foreach ($posts as $post)
+		{
+			if ($post->getContentType() !== \Szurubooru\Entities\Post::POST_TYPE_YOUTUBE)
+			{
+				$fullPath = $this->fileService->getFullPath($this->postService->getPostContentPath($post));
+				$mime = \Szurubooru\Helpers\MimeHelper::getMimeTypeFromFile($fullPath);
+				$post->setContentMimeType($mime);
+				$postDao->save($post);
+			}
+		}
+	}
+}
diff --git a/src/di.php b/src/di.php
index 9ba7b4d7..24fcf343 100644
--- a/src/di.php
+++ b/src/di.php
@@ -19,6 +19,7 @@ return [
 			$container->get(\Szurubooru\Upgrades\Upgrade01::class),
 			$container->get(\Szurubooru\Upgrades\Upgrade02::class),
 			$container->get(\Szurubooru\Upgrades\Upgrade03::class),
+			$container->get(\Szurubooru\Upgrades\Upgrade04::class),
 		];
 	}),