diff --git a/smwrappers/explore_mapping_parameters/wrapper.py b/smwrappers/explore_mapping_parameters/wrapper.py
index 334d0b5142c0fb70e2022a0d73245df4d206bdbe..90277fa52b33102f5ed19ff0fea9e69f4af7e906 100644
--- a/smwrappers/explore_mapping_parameters/wrapper.py
+++ b/smwrappers/explore_mapping_parameters/wrapper.py
@@ -55,12 +55,12 @@ echo -e "${{rate}}\\t{snakemake.params.these_settings}" >> {snakemake.params.rat
     return shell_commands
 
 with NamedTemporaryFile() as fastq, NamedTemporaryFile() as rates_record:
-    snakemake.params["fastq"] = fastq.name
+    snakemake.params.fastq = fastq.name
     # Take the first 10000 reads from the input
     shell(f"zcat {snakemake.input.fastq} | head -40000 | gzip > {fastq.name}")
-    snakemake.params["rates_record"] = rates_record.name
+    snakemake.params.rates_record = rates_record.name
     for settings in snakemake.params.settings:
-        snakemake.params["these_settings"] = settings
+        snakemake.params.these_settings = settings
         shell(mapping_command(snakemake.params.aligner))
     rates_record.seek(0)
     (best_rate, best_settings) = max(