diff --git a/src/utils.jl b/src/utils.jl
index d6764c1f..d4a632f3 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -263,7 +263,9 @@ function Base.convert(
         func.constants,
     )
 end
-function standard_form(func::MatrixVectorAffineFunction{T}) where {T}
+function standard_form(
+    func::MatrixVectorAffineFunction{<:AbstractMatrix{T}},
+) where {T}
     return convert(MOI.VectorAffineFunction{T}, func)
 end