diff --git a/src/likelihoods/negativebinomial.jl b/src/likelihoods/negativebinomial.jl
index 318887f..03c42d8 100644
--- a/src/likelihoods/negativebinomial.jl
+++ b/src/likelihoods/negativebinomial.jl
@@ -79,7 +79,9 @@ end
 
 @functor NegativeBinomialLikelihood
 
-(l::NegativeBinomialLikelihood)(fs::AbstractVector{<:Real}) = product_distribution(map(l, fs))
+function (l::NegativeBinomialLikelihood)(fs::AbstractVector{<:Real})
+    return product_distribution(map(l, fs))
+end
 
 @doc raw"""
     NBParamSuccess(successes)
diff --git a/test/runtests.jl b/test/runtests.jl
index 8bbc5cd..05528af 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -23,7 +23,7 @@ using Zygote
     end
     include("expectations.jl")
     @testset "Code quality (Aqua.jl)" begin
-        Aqua.test_all(GPLikelihoods; ambiguities = false)
+        Aqua.test_all(GPLikelihoods; ambiguities=false)
         # Ref https://github.com/JuliaTesting/Aqua.jl/issues/77
         Aqua.test_ambiguities(GPLikelihoods; recursive=false)
     end