diff --git a/.readthedocs.yml b/.readthedocs.yml
index 13ab9fa4..9a7bc196 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -1,5 +1,9 @@
 version: 2
 
+sphinx:
+  # Path to your Sphinx configuration file.
+  configuration: docs/sphinx/source/conf.py
+
 build:
   os: "ubuntu-24.04"
   tools:
diff --git a/rdtools/analysis_chains.py b/rdtools/analysis_chains.py
index e64ac4ec..9492badf 100644
--- a/rdtools/analysis_chains.py
+++ b/rdtools/analysis_chains.py
@@ -1292,3 +1292,6 @@ def _validate_keys(self):
         for key in self.keys():
             if key not in self.valid_keys:
                 raise KeyError(self._err_msg.format(key))
+
+    def __reduce__(self):
+        return (self.__class__, (self.valid_keys, dict(self)))
diff --git a/rdtools/normalization.py b/rdtools/normalization.py
index d5afacfc..23784a04 100644
--- a/rdtools/normalization.py
+++ b/rdtools/normalization.py
@@ -575,9 +575,9 @@ def _interpolate_series(time_series, target_index, max_timedelta=None,
     df = df.dropna()
 
     # convert to integer index and calculate the size of gaps in input
-    timestamps = df.index.view('int64')
-    df['timestamp'] = timestamps
-    df['gapsize_ns'] = df['timestamp'].diff()
+    timestamps = df.index.view("int64").copy()
+    df["timestamp"] = timestamps
+    df["gapsize_ns"] = df["timestamp"].diff()
     df.index = timestamps
 
     valid_indput_index = df.index.copy()