diff --git a/libs/HMMTest/src/allocations.jl b/libs/HMMTest/src/allocations.jl
index 6ba7d74..8deedaf 100644
--- a/libs/HMMTest/src/allocations.jl
+++ b/libs/HMMTest/src/allocations.jl
@@ -6,6 +6,7 @@ function test_allocations(
     seq_ends::AbstractVectorOrNTuple{Int},
     hmm_guess::Union{Nothing,AbstractHMM}=nothing,
 )
+    # making seq_ends a tuple disables multithreading
     seq_ends = ntuple(k -> seq_ends[k], Val(min(2, length(seq_ends))))
     control_seq = control_seq[1:last(seq_ends)]
 
@@ -51,7 +52,7 @@ function test_allocations(
             allocs_bw = @ballocated fit!(
                 hmm_guess_copy, $fb_storage, $obs_seq, $control_seq; seq_ends=$seq_ends
             ) evals = 1 samples = 1 setup = (hmm_guess_copy = deepcopy($hmm_guess))
-            @test_broken allocs_bw == 0
+            @test allocs_bw == 0
         end
     end
 end
diff --git a/src/types/hmm.jl b/src/types/hmm.jl
index 60d7bf1..9c1f47b 100644
--- a/src/types/hmm.jl
+++ b/src/types/hmm.jl
@@ -61,13 +61,23 @@ function StatsAPI.fit!(
 )
     (; γ, ξ) = fb_storage
     # Fit states
-    @threads for k in eachindex(seq_ends)
-        t1, t2 = seq_limits(seq_ends, k)
-        # use ξ[t2] as scratch space since it is zero anyway
-        scratch = ξ[t2]
-        fill!(scratch, zero(eltype(scratch)))
-        for t in t1:(t2 - 1)
-            scratch .+= ξ[t]
+    if seq_ends isa NTuple
+        for k in eachindex(seq_ends)
+            t1, t2 = seq_limits(seq_ends, k)
+            scratch = ξ[t2]  # use ξ[t2] as scratch space since it is zero anyway
+            fill!(scratch, zero(eltype(scratch)))
+            for t in t1:(t2 - 1)
+                scratch .+= ξ[t]
+            end
+        end
+    else
+        @threads for k in eachindex(seq_ends)
+            t1, t2 = seq_limits(seq_ends, k)
+            scratch = ξ[t2]  # use ξ[t2] as scratch space since it is zero anyway
+            fill!(scratch, zero(eltype(scratch)))
+            for t in t1:(t2 - 1)
+                scratch .+= ξ[t]
+            end
         end
     end
     fill!(hmm.init, zero(eltype(hmm.init)))