diff --git a/apps/dataset/sql/update_document_char_length.sql b/apps/dataset/sql/update_document_char_length.sql
index a09c8cab..4a4060cd 100644
--- a/apps/dataset/sql/update_document_char_length.sql
+++ b/apps/dataset/sql/update_document_char_length.sql
@@ -1,4 +1,7 @@
 UPDATE "document"
-SET "char_length" = ( SELECT "sum" ( "char_length" ( "content" ) ) FROM paragraph WHERE "document_id" = %s )
+SET "char_length" = ( SELECT CASE WHEN
+		"sum" ( "char_length" ( "content" ) ) IS NULL THEN
+			0 ELSE "sum" ( "char_length" ( "content" ) )
+		END FROM paragraph WHERE "document_id" = %s )
 WHERE
 	"id" = %s
\ No newline at end of file