diff --git a/Project.toml b/Project.toml
index 951e619..2bf4c65 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "CalculusWithJulia"
 uuid = "a2e0e22d-7d4c-5312-9169-8b992201a882"
-version = "0.1.3"
+version = "0.1.4"
 
 [deps]
 Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"
diff --git a/src/CalculusWithJulia.jl b/src/CalculusWithJulia.jl
index 4fa0ef2..c0b9bdd 100644
--- a/src/CalculusWithJulia.jl
+++ b/src/CalculusWithJulia.jl
@@ -79,7 +79,7 @@ function __init__()
     @require Plots="91a5bcdd-55d7-5caf-9e0b-520d859cae80" include("plots.jl") # could deprecate...
 end
 
-e = exp(1)
+const e = exp(1)
 export e
 
 export unzip, rangeclamp
diff --git a/src/sympy.jl b/src/sympy.jl
index 05aa1f4..633d08c 100644
--- a/src/sympy.jl
+++ b/src/sympy.jl
@@ -1,3 +1,6 @@
-gradient(ex::SymPy.Sym, vars::AbstractArray=SymPy.free_symbols(ex)) = diff.(ex, [vars...])
-divergence(F::Vector{SymPy.Sym}, vars=SymPy.free_symbols(F)) = sum(diff.(F, vars))
-curl(F::Vector{SymPy.Sym}, vars=SymPy.free_symbols(F)) = curl(F.jacobian(vars))
+gradient(ex::SymPy.Sym, vars::AbstractArray=SymPy.free_symbols(ex)) =
+    diff.(ex, [vars...])
+divergence(F::Vector{<:SymPy.Sym}, vars=SymPy.free_symbols(F)) =
+    sum(diff.(F, vars))
+curl(F::Vector{<:SymPy.Sym},       vars=SymPy.free_symbols(F)) =
+    curl(F.jacobian(vars))