diff --git a/Project.toml b/Project.toml
index 21aeb57..5b8f6f1 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "Roots"
 uuid = "f2b01f46-fcfa-551c-844a-d8ac1e96c665"
-version = "2.1.3"
+version = "2.1.4"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
diff --git a/src/convergence.jl b/src/convergence.jl
index b8a50dd..c33a11c 100644
--- a/src/convergence.jl
+++ b/src/convergence.jl
@@ -273,10 +273,10 @@ When the algorithm terminates, this function decides the stopped value or return
 function decide_convergence(
     M::AbstractNonBracketingMethod,
     F,
-    state::AbstractUnivariateZeroState,
+    state::AbstractUnivariateZeroState{T,S},
     options,
     val,
-)
+) where {T, S}
     xn0, xn1 = state.xn0, state.xn1
     fxn1 = state.fxn1
     val ∈ (:f_converged, :exact_zero, :converged) && return xn1
@@ -303,7 +303,7 @@ function decide_convergence(
         end
     end
 
-    NaN * xn1
+    nan(T) * xn1
 end
 
 # assumes stopped = :x_converged
diff --git a/src/hybrid.jl b/src/hybrid.jl
index 712bf5d..40d7e1a 100644
--- a/src/hybrid.jl
+++ b/src/hybrid.jl
@@ -42,7 +42,7 @@ function solve!(
     quad_ctr = 0
     flag = :not_converged
     ctr = 0
-    α = NaN * state.xn1
+    α = nan(typeof(state.xn1)) * state.xn1
     while true
         ctr += 1
         flag, converged = assess_convergence(M, state, options)
diff --git a/test/test_allocations.jl b/test/test_allocations.jl
index ed3ab56..4f941e1 100644
--- a/test/test_allocations.jl
+++ b/test/test_allocations.jl
@@ -93,6 +93,11 @@ import BenchmarkTools
         @test BenchmarkTools.@ballocated(solve(ZeroProblem($f, $x0), $M, $p)) == 0
         @test BenchmarkTools.@ballocated(solve(ZeroProblem($f, $x0), $M; p=$p)) == 0
     end
+
+    # issue #423 type instability
+    for M in Ms
+        @test @inferred solve(ZeroProblem(sin, 3.0f0)) ≈ pi
+    end
 end
 
 @testset "simple: zero allocations" begin