diff --git a/lib/private/Files/Type/Detection.php b/lib/private/Files/Type/Detection.php
index 64a7701011..f7a1aed41a 100644
--- a/lib/private/Files/Type/Detection.php
+++ b/lib/private/Files/Type/Detection.php
@@ -379,12 +379,15 @@ class Detection implements IMimeTypeDetector {
 		}
 
 		// Try only the first part of the filetype
-		$mimePart = substr($icon, 0, strpos($icon, '-'));
-		try {
-			$this->mimetypeIcons[$mimetype] = $this->urlGenerator->imagePath('core', 'filetypes/' . $mimePart . '.svg');
-			return $this->mimetypeIcons[$mimetype];
-		} catch (\RuntimeException $e) {
-			// Image for the first part of the mimetype not found
+
+		if (strpos($icon, '-')) {
+			$mimePart = substr($icon, 0, strpos($icon, '-'));
+			try {
+				$this->mimetypeIcons[$mimetype] = $this->urlGenerator->imagePath('core', 'filetypes/' . $mimePart . '.svg');
+				return $this->mimetypeIcons[$mimetype];
+			} catch (\RuntimeException $e) {
+				// Image for the first part of the mimetype not found
+			}
 		}
 
 		$this->mimetypeIcons[$mimetype] = $this->urlGenerator->imagePath('core', 'filetypes/file.svg');