diff --git a/src/BBOBFunction.jl b/src/BBOBFunction.jl
index c19ef0c..0c67550 100644
--- a/src/BBOBFunction.jl
+++ b/src/BBOBFunction.jl
@@ -117,7 +117,7 @@ end
 @define_x_and_f_opt(1)
 
 """ Sphere Function """
-f1(x) = ∑( (x[i] .- x1_opt[i])^2 for i=1:length(x) ) + f1_opt
+f1(x) = ∑( (x[i] - x1_opt[i])^2 for i=1:length(x) ) + f1_opt
 
 @BBOBFunction("Sphere", "sphere", 1)
 
@@ -432,4 +432,4 @@ end
 
 ## Compile time tests
 
-map(test_x_opt, BBOBFunctions)
\ No newline at end of file
+map(test_x_opt, BBOBFunctions)