diff --git a/src/SemiclassicalOrthogonalPolynomials.jl b/src/SemiclassicalOrthogonalPolynomials.jl
index 10f85a5..76ebcc3 100644
--- a/src/SemiclassicalOrthogonalPolynomials.jl
+++ b/src/SemiclassicalOrthogonalPolynomials.jl
@@ -174,6 +174,11 @@ function semiclassical_jacobimatrix(t, a, b, c)
     end
 end
 
+function semiclassical_jacobimatrix_raise_c_by_2(Q)
+    X = jacobimatrix(Q)
+    qr_jacobimatrix(Q.t*I-X,X)[1]
+end
+
 function semiclassical_jacobimatrix(Q::SemiclassicalJacobi, a, b, c)
     Δa = a-Q.a
     Δb = b-Q.b
@@ -202,7 +207,7 @@ function semiclassical_jacobimatrix(Q::SemiclassicalJacobi, a, b, c)
     elseif iszero(Δa) && isone(Δb/2) && iszero(Δc)
         qr_jacobimatrix(I-X,X)[1]
     elseif iszero(Δa) && iszero(Δb) && isone(Δc/2)
-        qr_jacobimatrix(Q.t*I-X,X)[1]
+        semiclassical_jacobimatrix_raise_c_by_2(Q)
     elseif isone(Δa) && iszero(Δb) && iszero(Δc)  # raising by 1
         cholesky_jacobimatrix(X,X)[1]
     elseif iszero(Δa) && isone(Δb) && iszero(Δc)
diff --git a/src/family.jl b/src/family.jl
index 49c724d..8cdd288 100644
--- a/src/family.jl
+++ b/src/family.jl
@@ -53,13 +53,21 @@ Base.broadcasted(::Type{SemiclassicalJacobi{T}}, t::Number, a::Union{AbstractUni
 _broadcast_getindex(a,k) = a[k]
 _broadcast_getindex(a::Number,k) = a
 
-function LazyArrays.cache_filldata!(P::SemiclassicalJacobiFamily, inds::AbstractUnitRange)
+function LazyArrays.cache_filldata!(P::SemiclassicalJacobiFamily{T,<:Number,<:Number,<:AbstractUnitRange}, inds::AbstractUnitRange) where T
+    t,a,b,c = P.t,P.a,P.b,P.c
+    for k in inds
+        Pprev = P.data[k-2]
+        P.data[k] = SemiclassicalJacobi{T}(Pprev.t, Pprev.a, Pprev.b, Pprev.c+2, semiclassical_jacobimatrix_raise_c_by_2(Pprev))
+    end
+    P
+end
+
+function LazyArrays.cache_filldata!(P::SemiclassicalJacobiFamily{<:Number,<:Number,<:AbstractUnitRange}, inds::AbstractUnitRange)
     t,a,b,c = P.t,P.a,P.b,P.c
-    isrange = P.b isa AbstractUnitRange
     for k in inds
         # If P.data[k-2] is not normalised (aka b = -1), cholesky fails. With the current design, this is only a problem if P.b
         # is a range since we can translate between polynomials that both have b = -1.
-        Pprev = (isrange && P.b[k-2] == -1) ? P.data[k-1] : P.data[k-2] # isrange && P.b[k-2] == -1 could also be !isnormalized(P.data[k-2])
+        Pprev = P.b[k-2] == -1 ? P.data[k-1] : P.data[k-2] # isrange && P.b[k-2] == -1 could also be !isnormalized(P.data[k-2])
         P.data[k] = SemiclassicalJacobi(t, _broadcast_getindex(a,k), _broadcast_getindex(b,k), _broadcast_getindex(c,k), Pprev)
     end
     P