diff --git a/src/gaspype/__init__.py b/src/gaspype/__init__.py
index 2cc0eff..579fbe5 100644
--- a/src/gaspype/__init__.py
+++ b/src/gaspype/__init__.py
@@ -240,7 +240,7 @@ class fluid_system:
             Array of gibbs free energy divided by RT (dimensionless)
         """
         return lookup(self._g_rt_array, t, self._t_offset)
-    
+
     def get_species_references(self) -> str:
         """Get a string with the references for all fluids of the fluid system
 
diff --git a/tests/test_fluid_references.py b/tests/test_fluid_references.py
index c2f9ead..b08f630 100644
--- a/tests/test_fluid_references.py
+++ b/tests/test_fluid_references.py
@@ -1,5 +1,6 @@
 import gaspype as gp
 
+
 def test_fluid_references():
     fs = gp.fluid_system('Cl, CH4, H2O, C2H6, C3H8')
 
@@ -9,4 +10,4 @@ H2O         : Hf:Cox,1989. Woolley,1987. TRC(10/88) tuv25. [g 8/89]
 C2H6        : Ethane. Pamidimukkala,1982. [g 7/00]
 C3H8        : Hf:TRC(10/85) w1350. Chao,1973. [g 2/00]"""
 
-    assert reference_string == fs.get_species_references(), 'fs.get_species_references() == ' + fs.get_species_references()
\ No newline at end of file
+    assert reference_string == fs.get_species_references(), 'fs.get_species_references() == ' + fs.get_species_references()