diff --git a/ev_to_dicom/ev_to_dcm.py b/ev_to_dicom/ev_to_dcm.py
index a991330..1b56867 100644
--- a/ev_to_dicom/ev_to_dcm.py
+++ b/ev_to_dicom/ev_to_dcm.py
@@ -41,7 +41,7 @@ def ev_files_to_dcm_file(study_uid, series_uid, series_number, image_number, inp
 	file_meta = FileMetaDataset()
 	
 	if metadata['metadata']['modality'] == 'US':
-		if len(pixel_datas) == 0:
+		if len(pixel_datas) == 1:
 			file_meta.MediaStorageSOPClassUID = '1.2.840.10008.5.1.4.1.1.6.1'  # Ultrasound Image Storage
 		else:
 			file_meta.MediaStorageSOPClassUID = '1.2.840.10008.5.1.4.1.1.3.1'  # Ultrasound Multi-frame Image Storage