diff --git a/scripts/build_biomass_potentials.py b/scripts/build_biomass_potentials.py
index 27b2e0a39..d7c467cf6 100644
--- a/scripts/build_biomass_potentials.py
+++ b/scripts/build_biomass_potentials.py
@@ -263,7 +263,7 @@ def convert_nuts2_to_regions(bio_nuts2, regions):
     df.to_csv(snakemake.output.biomass_potentials_all)
 
     grouper = {v: k for k, vv in params["classes"].items() for v in vv}
-    df = df.T.groupby(grouper).sum()
+    df = df.T.groupby(grouper).sum().T
 
     df *= 1e6  # TWh/a to MWh/a
     df.index.name = "MWh/a"