diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 48915f4c..826a4819 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -39,7 +39,7 @@ repos:
 
   # Make docstrings PEP 257 compliant
 - repo: https://github.com/PyCQA/docformatter
-  rev: v1.6.5
+  rev: v1.7.2
   hooks:
   - id: docformatter
     args: ["--in-place", "--make-summary-multi-line", "--pre-summary-newline"]
diff --git a/README.md b/README.md
index 02cc3163..79cdfa65 100644
--- a/README.md
+++ b/README.md
@@ -96,7 +96,7 @@ repository](https://doi.org/10.5281/zenodo.3601881).
 We strongly welcome anyone interested in contributing to this project. If you have any ideas, suggestions or encounter problems, feel invited to file issues or make pull requests on GitHub.
 -   In case of code-related **questions**, please post on [stack overflow](https://stackoverflow.com/questions/tagged/pypsa).
 -   For non-programming related and more general questions please refer to the [mailing list](https://groups.google.com/group/pypsa).
--   To **discuss** with other PyPSA users, organise projects, share news, and get in touch with the community you can use the [discord server](https://discord.gg/JTdvaEBb).
+-   To **discuss** with other PyPSA users, organise projects, share news, and get in touch with the community you can use the [discord server](https://discord.com/invite/AnuJBk23FU).
 -   For **bugs and feature requests**, please use the [PyPSA-Eur Github Issues page](https://github.com/PyPSA/pypsa-eur/issues).
 
 # Licence
diff --git a/scripts/_helpers.py b/scripts/_helpers.py
index 2cc9a05a..512cb87a 100644
--- a/scripts/_helpers.py
+++ b/scripts/_helpers.py
@@ -385,10 +385,11 @@ def mock_snakemake(rulename, configfiles=[], **wildcards):
 
 
 def override_component_attrs(directory):
-    """Tell PyPSA that links can have multiple outputs by
-    overriding the component_attrs. This can be done for
-    as many buses as you need with format busi for i = 2,3,4,5,....
-    See https://pypsa.org/doc/components.html#link-with-multiple-outputs-or-inputs
+    """
+    Tell PyPSA that links can have multiple outputs by overriding the
+    component_attrs. This can be done for as many buses as you need with format
+    busi for i = 2,3,4,5,.... See https://pypsa.org/doc/components.html#link-
+    with-multiple-outputs-or-inputs.
 
     Parameters
     ----------
diff --git a/scripts/build_retro_cost.py b/scripts/build_retro_cost.py
index 8473be7a..ac7eb4ae 100644
--- a/scripts/build_retro_cost.py
+++ b/scripts/build_retro_cost.py
@@ -698,8 +698,8 @@ def get_solar_gains_per_year(window_area):
 
 def map_to_lstrength(l_strength, df):
     """
-    renames column names from a pandas dataframe to map tabula retrofitting
-    strengths [2 = moderate, 3 = ambitious] to l_strength
+    Renames column names from a pandas dataframe to map tabula retrofitting
+    strengths [2 = moderate, 3 = ambitious] to l_strength.
     """
     middle = len(l_strength) // 2
     map_to_l = pd.MultiIndex.from_arrays(
diff --git a/scripts/cluster_network.py b/scripts/cluster_network.py
index b86bb225..db0fb2c2 100644
--- a/scripts/cluster_network.py
+++ b/scripts/cluster_network.py
@@ -424,7 +424,10 @@ def clustering_for_n_clusters(
             n.links.eval("underwater_fraction * length").div(nc.links.length).dropna()
         )
         nc.links["capital_cost"] = nc.links["capital_cost"].add(
-            (nc.links.length - n.links.length).clip(lower=0).mul(extended_link_costs),
+            (nc.links.length - n.links.length)
+            .clip(lower=0)
+            .mul(extended_link_costs)
+            .dropna(),
             fill_value=0,
         )
 
diff --git a/scripts/prepare_sector_network.py b/scripts/prepare_sector_network.py
index 54ab1f94..8b8b7d80 100644
--- a/scripts/prepare_sector_network.py
+++ b/scripts/prepare_sector_network.py
@@ -1105,7 +1105,11 @@ def add_storage_and_grids(n, costs):
     cavern_types = snakemake.params["sector"]["hydrogen_underground_storage_locations"]
     h2_caverns = pd.read_csv(snakemake.input.h2_cavern, index_col=0)
 
-    if not h2_caverns.empty and options["hydrogen_underground_storage"]:
+    if (
+        not h2_caverns.empty
+        and options["hydrogen_underground_storage"]
+        and set(cavern_types).intersection(h2_caverns.columns)
+    ):
         h2_caverns = h2_caverns[cavern_types].sum(axis=1)
 
         # only use sites with at least 2 TWh potential