diff --git a/src/multi_configurational_equations.jl b/src/multi_configurational_equations.jl
index 86927d6..467f67c 100644
--- a/src/multi_configurational_equations.jl
+++ b/src/multi_configurational_equations.jl
@@ -164,6 +164,9 @@ function Base.diff(E::EM, orbitals::VO; verbosity=0) where {EM<:EnergyExpression
         isnothing(p) || ProgressMeter.next!(p)
         eq
     end
+    if !(equations isa AbstractVector)
+        equations = [equations]
+    end
 
     vd = collect(values(integrals.data))
     verbosity > 3 && @info "Integrals" integrals.data filter(∉(1:length(integrals.data)), vd)