diff --git a/idc_index/index.py b/idc_index/index.py
index 3c055c7..fe84ddb 100644
--- a/idc_index/index.py
+++ b/idc_index/index.py
@@ -779,6 +779,11 @@ def _validate_update_manifest_and_get_download_size(
         # Rename the column
         manifest_df.columns = ["manifest_cp_cmd"]
 
+        # remove all rows that do not contain an S3 URL
+        manifest_df = manifest_df[
+            manifest_df["manifest_cp_cmd"].str.contains(r"s3://", na=False)
+        ]
+
         # create a copy of the index
         index_df_copy = self.index[
             [
@@ -916,7 +921,9 @@ def _validate_update_manifest_and_get_download_size(
                 REGEXP_EXTRACT(manifest_cp_cmd, '(?:.*?\\/){{3}}([^\\/?#]+)', 1) AS manifest_crdc_series_uuid,
                 REGEXP_REPLACE(regexp_replace(manifest_cp_cmd, 'cp ', ''), '\\s[^\\s]*$', '') AS s3_url,
             FROM
-                manifest_df )
+                manifest_df
+            WHERE
+                REGEXP_REPLACE(regexp_replace(manifest_cp_cmd, 'cp ', ''), '\\s[^\\s]*$', '') IS NOT NULL)
             SELECT
                 seriesInstanceuid,
                 index_crdc_series_uuid,
diff --git a/tests/study_manifest_aws.s5cmd b/tests/study_manifest_aws.s5cmd
index 86631b3..765586d 100644
--- a/tests/study_manifest_aws.s5cmd
+++ b/tests/study_manifest_aws.s5cmd
@@ -1,6 +1,7 @@
 # To download the files in this manifest, first install s5cmd (https://github.com/peak/s5cmd),
 # then run the following command:
 # s5cmd --no-sign-request --endpoint-url https://s3.amazonaws.com run study_manifest_aws.s5cmd
+study_manifest_cp_command
 cp s3://idc-open-data/28621ba9-1aca-4aab-a2a1-f6d2c3e2ab19/* .
 cp s3://idc-open-data/f0b76401-c6d1-4b61-a5fd-3fa596e6cc41/* .
 cp s3://idc-open-data/4ea3bbe6-98da-4b92-abe6-2ee18927e3c9/* .