diff --git a/preprocessing/nextclade/src/loculus_preprocessing/backend.py b/preprocessing/nextclade/src/loculus_preprocessing/backend.py
index ae249787b..aafa1352e 100644
--- a/preprocessing/nextclade/src/loculus_preprocessing/backend.py
+++ b/preprocessing/nextclade/src/loculus_preprocessing/backend.py
@@ -16,6 +16,8 @@
 from .config import Config
 from .datatypes import (
     ProcessedEntry,
+    UnprocessedData,
+    UnprocessedEntry,
 )
 
 
@@ -66,7 +68,31 @@ def get_jwt(config: Config) -> str:
         raise Exception(error_msg)
 
 
-def fetch_unprocessed_sequences(etag: str, config: Config) -> tuple[str, str]:
+def parse_ndjson(ndjson_data: str) -> Sequence[UnprocessedEntry]:
+    entries = []
+    for json_str in ndjson_data.split("\n"):
+        if len(json_str) == 0:
+            continue
+        # Loculus currently cannot handle non-breaking spaces.
+        json_str_processed = json_str.replace("\N{NO-BREAK SPACE}", " ")
+        json_object = json.loads(json_str_processed)
+        unprocessed_data = UnprocessedData(
+            submitter=json_object["submitter"],
+            metadata=json_object["data"]["metadata"],
+            unalignedNucleotideSequences=json_object["data"]["unalignedNucleotideSequences"],
+        )
+        entry = UnprocessedEntry(
+            accessionVersion=f"{json_object['accession']}.{
+                json_object['version']}",
+            data=unprocessed_data,
+        )
+        entries.append(entry)
+    return entries
+
+
+def fetch_unprocessed_sequences(
+    etag: str, config: Config
+) -> tuple[str, Sequence[UnprocessedEntry] | None]:
     n = config.batch_size
     url = config.backend_host.rstrip("/") + "/extract-unprocessed-data"
     logging.debug(f"Fetching {n} unprocessed sequences from {url}")
@@ -78,7 +104,7 @@ def fetch_unprocessed_sequences(etag: str, config: Config) -> tuple[str, str]:
         case HTTPStatus.NOT_MODIFIED:
             return etag, None
         case HTTPStatus.OK:
-            return response.headers["ETag"], response.text
+            return response.headers["ETag"], parse_ndjson(response.text)
         case HTTPStatus.UNPROCESSABLE_ENTITY:
             logging.debug(f"{response.text}.\nSleeping for a while.")
             time.sleep(60 * 1)
diff --git a/preprocessing/nextclade/src/loculus_preprocessing/prepro.py b/preprocessing/nextclade/src/loculus_preprocessing/prepro.py
index d49e15d47..c659b050d 100644
--- a/preprocessing/nextclade/src/loculus_preprocessing/prepro.py
+++ b/preprocessing/nextclade/src/loculus_preprocessing/prepro.py
@@ -52,28 +52,6 @@
 # Functions related to reading and writing files
 
 
-def parse_ndjson(ndjson_data: str) -> Sequence[UnprocessedEntry]:
-    entries = []
-    for json_str in ndjson_data.split("\n"):
-        if len(json_str) == 0:
-            continue
-        # Loculus currently cannot handle non-breaking spaces.
-        json_str_processed = json_str.replace("\N{NO-BREAK SPACE}", " ")
-        json_object = json.loads(json_str_processed)
-        unprocessed_data = UnprocessedData(
-            submitter=json_object["submitter"],
-            metadata=json_object["data"]["metadata"],
-            unalignedNucleotideSequences=json_object["data"]["unalignedNucleotideSequences"],
-        )
-        entry = UnprocessedEntry(
-            accessionVersion=f"{json_object['accession']}.{
-                json_object['version']}",
-            data=unprocessed_data,
-        )
-        entries.append(entry)
-    return entries
-
-
 def parse_nextclade_tsv(
     amino_acid_insertions: defaultdict[
         AccessionVersion, defaultdict[GeneName, list[AminoAcidInsertion]]