diff --git a/htsinfer/mapping.py b/htsinfer/mapping.py
index 9a5d4e6a..cb53f7a5 100644
--- a/htsinfer/mapping.py
+++ b/htsinfer/mapping.py
@@ -95,7 +95,7 @@ def subset_transcripts_by_organism(self) -> Path:
         """
         LOGGER.debug(f"Subsetting transcripts for: {self.library_source}")
 
-        outfile = self.tmp_dir / f"{self.library_source}.fasta"
+        outfile = self.tmp_dir / "transcripts_subset.fasta"
 
         def yield_filtered_seqs():
             """Generator yielding sequence records for specified sources.
diff --git a/tests/test_mapping.py b/tests/test_mapping.py
index 6492ed32..33798bed 100644
--- a/tests/test_mapping.py
+++ b/tests/test_mapping.py
@@ -84,7 +84,7 @@ def test_subset_transcripts_by_organism(self, tmpdir):
         test_instance = Mapping(config=CONFIG)
         results = test_instance.subset_transcripts_by_organism()
         filtered_organisms_transcripts = \
-            tmpdir / f"{CONFIG.results.library_source}.fasta"
+            tmpdir / "transcripts_subset.fasta"
         assert results == filtered_organisms_transcripts
 
     def test_subset_transcripts_by_organism_file_problem(self, tmpdir):
@@ -111,7 +111,7 @@ def test_subset_transcripts_by_organism_invalid_fasta(self, tmpdir):
         test_instance = Mapping(config=CONFIG)
         results = test_instance.subset_transcripts_by_organism()
         filtered_organisms_transcripts = \
-            tmpdir / f"{CONFIG.results.library_source}.fasta"
+            tmpdir / "transcripts_subset.fasta"
         assert results == filtered_organisms_transcripts
 
     def test_get_fasta_size(self, tmpdir):