diff --git a/pes_to_spec/config.py b/pes_to_spec/config.py
index d4dfab585ed06eb38ed2067df70df72bb177513e..d51c58ca89504cce7dc0f869e751963b67e2999a 100644
--- a/pes_to_spec/config.py
+++ b/pes_to_spec/config.py
@@ -66,7 +66,7 @@ class VSConfig(object):
                 if m is not None and len(m.groups()) >= 1:
                     name = m.groups()[0]
                     out.voltage_mean[name] = run[VSConfig.voltage_source, f"{name}.value"].ndarray().mean()
-                    out.voltage_std[name] = run[VSConfguration.voltage_source, f"{name}.value"].ndarray().std()
+                    out.voltage_std[name] = run[VSConfig.voltage_source, f"{name}.value"].ndarray().std()
 
         for gas in VSConfig.gas_sources:
             # check if this gas source is interlocked
@@ -90,7 +90,7 @@ class VSConfig(object):
             errors += [f"Multiple gas active during the data: {self.gas_active}."]
         return errors
 
-    def __sub__(self, other: VSConfig) -> VSConfig:
+    def __sub__(self, other: 'VSConfig') -> 'VSConfig':
         """
         Take difference between two configuratons.
         """
@@ -101,7 +101,7 @@ class VSConfig(object):
         diff.gas_active = set(self.gas_active).difference(set(other.gas_active))
         return diff
 
-    def __eq__(self, other) -> bool:
+    def __eq__(self, other: 'VSConfig') -> bool:
         """
         Check if two configurations match.
         """