diff --git a/lib/private/preview/movies.php b/lib/private/preview/movies.php
index ac771deb41..71cd3bae05 100644
--- a/lib/private/preview/movies.php
+++ b/lib/private/preview/movies.php
@@ -18,7 +18,7 @@ function findBinaryPath($program) {
 
 // movie preview is currently not supported on Windows
 if (!\OC_Util::runningOnWindows()) {
-	$isExecEnabled = !in_array('exec', explode(', ', ini_get('disable_functions')));
+	$isExecEnabled = \OC_Helper::is_function_enabled('exec');
 	$ffmpegBinary = null;
 	$avconvBinary = null;
 
diff --git a/lib/private/preview/office.php b/lib/private/preview/office.php
index 318ab51f85..7a4826c76e 100644
--- a/lib/private/preview/office.php
+++ b/lib/private/preview/office.php
@@ -7,7 +7,7 @@
  */
 //both, libreoffice backend and php fallback, need imagick
 if (extension_loaded('imagick')) {
-	$isShellExecEnabled = !in_array('shell_exec', explode(', ', ini_get('disable_functions')));
+	$isShellExecEnabled = \OC_Helper::is_function_enabled('shell_exec');
 
 	// LibreOffice preview is currently not supported on Windows
 	if (!\OC_Util::runningOnWindows()) {