diff --git a/lib/private/legacy/OC_Image.php b/lib/private/legacy/OC_Image.php
index 1e00b606ea0..9eb9c2b8dcb 100644
--- a/lib/private/legacy/OC_Image.php
+++ b/lib/private/legacy/OC_Image.php
@@ -662,6 +662,42 @@ class OC_Image implements \OCP\IImage {
 		return $this->resource;
 	}
 
+	/**
+	 * Get the correct file type from a buffered image
+	 *
+	 * @param string $buffer The image data to analyze
+	 * @return void
+	 */
+	private function updateImageTypes($buffer) {
+		if ($this->valid()) {
+			$finfo = new finfo(FILEINFO_MIME_TYPE);
+			$this->mimeType = $finfo->buffer($buffer);
+			switch ($this->mimeType) {
+				case 'image/gif':
+					$this->imageType = IMAGETYPE_GIF;
+					break;
+				case 'image/jpeg':
+					$this->imageType = IMAGETYPE_JPEG;
+					break;
+				case 'image/png':
+					$this->imageType = IMAGETYPE_PNG;
+					break;
+				case 'image/xbm':
+					$this->imageType = IMAGETYPE_XBM;
+					break;
+				case 'image/vnd.wap.wbmp':
+					$this->imageType = IMAGETYPE_WBMP;
+					break;
+				case 'image/bmp':
+					$this->imageType = IMAGETYPE_BMP;
+					break;
+				case 'image/webp':
+					$this->imageType = IMAGETYPE_WEBP;
+					break;
+			}
+		}
+	}
+
 	/**
 	 * Loads an image from a string of data.
 	 *
@@ -673,13 +709,11 @@ class OC_Image implements \OCP\IImage {
 			return false;
 		}
 		$this->resource = @imagecreatefromstring($str);
-		if ($this->fileInfo) {
-			$this->mimeType = $this->fileInfo->buffer($str);
-		}
 		if (is_resource($this->resource)) {
 			imagealphablending($this->resource, false);
 			imagesavealpha($this->resource, true);
 		}
+		$this->updateImageTypes($str);
 
 		if (!$this->resource) {
 			$this->logger->debug('OC_Image->loadFromFile, could not load', ['app' => 'core']);
@@ -701,9 +735,7 @@ class OC_Image implements \OCP\IImage {
 		$data = base64_decode($str);
 		if ($data) { // try to load from string data
 			$this->resource = @imagecreatefromstring($data);
-			if ($this->fileInfo) {
-				$this->mimeType = $this->fileInfo->buffer($data);
-			}
+			$this->updateImageTypes($data);
 			if (!$this->resource) {
 				$this->logger->debug('OC_Image->loadFromBase64, could not load', ['app' => 'core']);
 				return false;