diff --git a/scripts/build_ammonia_production.py b/scripts/build_ammonia_production.py
index 1bcdf9ae..bfcfaf02 100644
--- a/scripts/build_ammonia_production.py
+++ b/scripts/build_ammonia_production.py
@@ -8,6 +8,7 @@ Build historical annual ammonia production per country in ktonNH3/a.
 
 import country_converter as coco
 import pandas as pd
+import numpy as np
 
 cc = coco.CountryConverter()
 
@@ -30,8 +31,12 @@ if __name__ == "__main__":
     ammonia.index = cc.convert(ammonia.index, to="iso2")
 
     years = [str(i) for i in range(2013, 2018)]
-    countries = ammonia.index.intersection(snakemake.params.countries)
-    ammonia = ammonia.loc[countries, years].astype(float)
+
+    ammonia = ammonia[years]
+    ammonia.replace("--",
+                    np.nan,
+                    inplace=True)
+    ammonia = ammonia.astype(float)
 
     # convert from ktonN to ktonNH3
     ammonia *= 17 / 14