diff --git a/Project.toml b/Project.toml
index 00c9114..4b52524 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "MixedModelsSim"
 uuid = "d5ae56c5-23ca-4a1f-b505-9fc4796fc1fe"
 authors = ["Phillip Alday", "Douglas Bates", "Lisa DeBruine", "Reinhold Kliegl"]
-version = "0.2.8"
+version = "0.2.9"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
diff --git a/src/utilities.jl b/src/utilities.jl
index 5ef65f7..c291dba 100644
--- a/src/utilities.jl
+++ b/src/utilities.jl
@@ -281,6 +281,7 @@ random effects.
     [`update!`](@ref) requires.
 """
 function create_re(sigmas...; corrmat=nothing)
+    all(>=(0), sigmas) || throw(ArgumentError("all σs must be non negative"))
     ss = Diagonal([sigmas...])
 
     isnothing(corrmat) ? LowerTriangular(ss) : ss * cholesky(Symmetric(corrmat, :L)).L