diff --git a/src/Utilities/functions.jl b/src/Utilities/functions.jl
index 2d558f92e4..a87c3a8d9b 100644
--- a/src/Utilities/functions.jl
+++ b/src/Utilities/functions.jl
@@ -592,7 +592,7 @@ end
 Type of functions obtained by indexing objects obtained by calling `eachscalar`
 on functions of type `F`.
 """
-function scalar_type end
+scalar_type(::Type{<:MOI.AbstractVectorFunction}) = Any  # A default fallback
 
 scalar_type(::Type{<:AbstractVector{T}}) where {T} = T