diff --git a/manuscript/article.qmd b/manuscript/article.qmd
index 439eff1..361e405 100644
--- a/manuscript/article.qmd
+++ b/manuscript/article.qmd
@@ -593,6 +593,7 @@ the overall output volume strongly increased during this period.
 ```{python}
 #| label: fig-publications-per-year
 #| fig-cap: Publications per year
+from typing import cast
 
 df_study_years = (
     df.groupby(["author", "year", "title"])
@@ -602,6 +603,8 @@ df_study_years = (
     ["year"].value_counts()
     .sort_index()
 )
+df_study_years = cast(pd.DataFrame, df_study_years) # fix potential type errors
+
 # use order to ensure all years are displayed, even ones without values
 years_range = list(range(df_study_years.index.min(), df_study_years.index.max()+1))
 ax = sns.barplot(df_study_years, order=years_range)