diff --git a/scripts/build_powerplants.py b/scripts/build_powerplants.py
index f25f111b..cefc0ee5 100755
--- a/scripts/build_powerplants.py
+++ b/scripts/build_powerplants.py
@@ -98,13 +98,13 @@ def add_custom_powerplants(ppl, custom_powerplants, custom_ppl_query=False):
 
 
 def replace_natural_gas_technology(df):
-    mapping = {"Steam Turbine": "OCGT", "Combustion Engine": "OCGT"}
-    tech = df.Technology.replace(mapping).fillna("OCGT")
-    return df.Technology.where(df.Fueltype != "Natural Gas", tech)
+    mapping = {"Steam Turbine": "CCGT", "Combustion Engine": "OCGT"}
+    tech = df.Technology.replace(mapping).fillna("CCGT")
+    return df.Technology.mask(df.Fueltype == "Natural Gas", tech)
 
 
 def replace_natural_gas_fueltype(df):
-    return df.Fueltype.where(df.Fueltype != "Natural Gas", df.Technology)
+    return df.Fueltype.mask(df.Technology == "OCGT" | df.Technology == "CCGT", "Natural Gas")
 
 
 if __name__ == "__main__":