diff --git a/src/ScaleAperture.jl b/src/ScaleAperture.jl
index 17c9eb6..c5e9043 100644
--- a/src/ScaleAperture.jl
+++ b/src/ScaleAperture.jl
@@ -10,9 +10,8 @@ https://www.jeos.org/index.php/jeos_rp/article/view/07012
 
 function Π(v::Vector{T}, ε::T) where T <: Float64
     !(0.0 ≤ ε ≤ 1.0) && error("Bounds: 0.0 ≤ ε ≤ 1.0\n")
-    j_max::Int = length(v) - 1
-    n_max::Int = get_n(j_max)
-    v2 = Vector{Float64}(undef, j_max + 1)
+    len, n_max = validate_length(v)
+    v2 = Vector{Float64}(undef, len)
     n = 0
     m = 0
     for i in eachindex(v)
diff --git a/src/TransformAperture.jl b/src/TransformAperture.jl
index 9191f3c..ba140e7 100644
--- a/src/TransformAperture.jl
+++ b/src/TransformAperture.jl
@@ -16,8 +16,7 @@ const ei = cis # ei(x) = exp(im*x)
 function S(v::Vector{T}, ε::T, δ::Complex{T}, ϕ::T, ω::Tuple{T,T}) where T <: Float64
     !(0.0 ≤ ε + abs(δ) ≤ 1.0) && error("Bounds: 0.0 ≤ ε + |δ| ≤ 1.0\n")
     !(0.0 < ω[1] ≤ 1.0) && error("Bounds: 0.0 < ω[1] ≤ 1.0\n")
-    len = length(v)
-    n_max = get_n(len - 1)
+    len, n_max = validate_length(v)
     remap = Dict{Tuple{Int, Int}, Int}()
     order = Tuple{Int, Int, Int}[]
     # normalization factors for complex Zernike polynomials
diff --git a/src/Zernike.jl b/src/Zernike.jl
index c3ba93e..2ac4dfb 100644
--- a/src/Zernike.jl
+++ b/src/Zernike.jl
@@ -102,6 +102,7 @@ function noll_to_j(noll::Int)
 end
 
 function standardize!(noll::Vector)
+    validate_length(noll)
     invpermute!(noll, [noll_to_j(i) + 1 for i in eachindex(noll)])
 end
 
@@ -130,6 +131,21 @@ function standardize(fringe::Vector)
     return a
 end
 
+function validate_length(v::Vector)
+    len = length(v)
+    j_max = len - 1
+    n_max = get_n(j_max)
+    if j_max ≠ get_j(n_max, n_max)
+        error(
+            """
+            Invalid number of coefficients.
+            Coefficients for Zernike polynomials up to m = n_max, n = n_max required.
+            """
+        )
+    end
+    return len, n_max
+end
+
 function radicand(m, n)
     # Kronecker delta δ_{m0}
     δ(m) = m == 0