diff --git a/src/GrpAb/stable_sub.jl b/src/GrpAb/stable_sub.jl
index 193cfa8795..ce88395804 100644
--- a/src/GrpAb/stable_sub.jl
+++ b/src/GrpAb/stable_sub.jl
@@ -299,7 +299,7 @@ function minimal_submodules(M::ZpnGModule, ord::Int=-1)
   v = Int[M.p^(valuation(S.V.snf[i], M.p)-1) for i=1:ngens(S.V)]
   W = matrix_space(R, 1, ngens(M.V); cached=false)
   for z = 1:length(list)
-    list[z] = vcat(zzModMatrix[W((mS(S.V(ZZRingElem[lift(list_sub[z][k,i])*v[i] for i=1:ngens(S.V)]))).coeff) for k=1:nrows(list_sub[z])])
+    list[z] = reduce(vcat, [W((mS(S.V(ZZRingElem[lift(list_sub[z][k,i])*v[i] for i=1:ngens(S.V)]))).coeff) for k=1:nrows(list_sub[z])])
   end
   return list
 
diff --git a/src/Misc/jordan.jl b/src/Misc/jordan.jl
index 449adafaf2..e0236adeeb 100644
--- a/src/Misc/jordan.jl
+++ b/src/Misc/jordan.jl
@@ -849,7 +849,7 @@ function simultaneous_diagonalization(L::Vector{S}; check::Bool = true) where S
 
   # Compute transformation matrix
   CE = common_eigenspaces(L, side = :left)
-  A =  Hecke.vcat(collect(values(CE)))
+  A = reduce(vcat, values(CE))
 
   # Compute diagonal forms
   D = [ zero_matrix(base_ring(L[1]), nrows(L[1]), ncols(L[1])) for i = 1:length(L) ]
diff --git a/src/NumField/Subfields.jl b/src/NumField/Subfields.jl
index 1e1d700d25..b402aec3a8 100644
--- a/src/NumField/Subfields.jl
+++ b/src/NumField/Subfields.jl
@@ -334,7 +334,7 @@ function fixed_field(K::AnticNumberField, A::Vector{NfToNfMor}; simplify::Bool =
   if length(ar_mat) == 0
     return K, id_hom(K)
   else
-    bigmatrix = hcat(ar_mat)
+    bigmatrix = reduce(hcat, ar_mat)
     k, Ker = kernel(bigmatrix, side = :left)
     bas = Vector{elem_type(K)}(undef, k)
     if simplify
@@ -397,7 +397,7 @@ function fixed_field(K::NfRel, A::Vector{T}; simplify::Bool = true) where {T <:
   if length(ar_mat) == 0
     return K, id_hom(K)
   else
-    bigmatrix = hcat(ar_mat)
+    bigmatrix = reduce(hcat, ar_mat)
     k, Ker = kernel(bigmatrix, side = :left)
     bas = Vector{elem_type(K)}(undef, k)
     for i in 1:k