diff --git a/matlab/write_pac_mce_expectations.m b/matlab/write_pac_mce_expectations.m
index da8c7b84547fac449d4460319c43c2cc31e851f3..2ed0d5e48583c065ebc058c92a8e1c8d838c7f32 100644
--- a/matlab/write_pac_mce_expectations.m
+++ b/matlab/write_pac_mce_expectations.m
@@ -137,7 +137,7 @@ for i=1:length(alphaid)-1
         for k=length(transformations):-1:1
             variable = sprintf('%s(%s)', transformations{k}, variable);
         end
-        expression = sprintf('%s-(%s)*diff(%s(%i))', expression, tmp, variable);
+        expression = sprintf('%s-(%s)*diff(%s)', expression, tmp, variable);
     end
 end