diff -u b/core/modules/file/migration_templates/d7_file.yml b/core/modules/file/migration_templates/d7_file.yml
--- b/core/modules/file/migration_templates/d7_file.yml
+++ b/core/modules/file/migration_templates/d7_file.yml
@@ -10,8 +10,14 @@
   fid: fid
   filename: filename
   source_full_path:
-    plugin: urlencode
-    source: filepath
+    -
+      plugin: concat
+      delimiter: /
+      source:
+        - constants/source_base_path
+        - filepath
+    -
+      plugin: urlencode
   uri:
     plugin: file_copy
     source: