diff --git a/src/specapi.jl b/src/specapi.jl
index 7d43ee1f599..a6ee0c476f7 100644
--- a/src/specapi.jl
+++ b/src/specapi.jl
@@ -704,10 +704,10 @@ function update_layoutable!(block::T, plot_obs, old_spec::BlockSpec, spec::Block
             tightlimits!(block)
         end
     end
-    for observer in spec.then_observers
+    for observer in old_spec.then_observers
         Observables.off(observer)
     end
-    empty!(spec.then_observers)
+    empty!(old_spec.then_observers)
     if hasproperty(spec, :xaxislinks)
         empty!(spec.xaxislinks)
     end
diff --git a/test/specapi.jl b/test/specapi.jl
index ba1389d1ef7..056e9962b5c 100644
--- a/test/specapi.jl
+++ b/test/specapi.jl
@@ -129,3 +129,44 @@ end
     @test !haskey(pl, :clamp_bincounts)
     @test !haskey(pl.plots[1], :clamp_bincounts)
 end
+
+@testset "then observer clean up" begin
+    ax = S.Axis(title="interaction")
+    ax.then(axis-> on(println, events(axis).mouseposition))
+    gl = S.GridLayout(ax)
+
+    f, _, pl = plot(gl)
+    real_ax = f.content[1]
+    mpos = events(real_ax).mouseposition
+    @test length(mpos.listeners) == 2
+    @test mpos.listeners[end][2] === println
+    @test length(ax.then_observers) == 1
+    @test first(ax.then_observers).f === println
+
+    pl[1] = S.GridLayout(S.Axis(title="interaction"))
+    @test real_ax === f.content[1] # re-use axis
+    @test length(mpos.listeners) == 1
+    @test mpos.listeners[1][2] !== println
+end
+
+@testset "Blockspec re-use" begin
+    ax1 = S.Axis(; title="Title 1")
+    ax2 = S.Axis(; title="Title 2")
+    ax3 = S.Axis(; title="Title 3")
+    axes = [ax1, ax2, ax3]
+    gl = S.GridLayout(axes)
+    f, _, pl = plot(gl)
+    real_axes = copy(f.content[1:3])
+    @test map(x-> x.title[], real_axes) == ["Title $i" for i in 1:3]
+    pl[1] = S.GridLayout(reverse(axes))
+    rev_axes = copy(f.content[1:3])
+    c_axes = map(x-> x.content, f.layout.content)
+    # Axis get reversed in layout, but not in f.content
+    @test rev_axes == reverse(c_axes)
+    @test map(x-> x.title[], rev_axes) == ["Title $i" for i in 1:3]
+    @test all(((a, b),) -> a === b, zip(rev_axes, real_axes))
+    @test all(((a, b),) -> a.title[] == b.title[], zip(rev_axes, real_axes))
+    pl[1] =  S.GridLayout()
+    @test isempty(f.content)
+    @test isempty(f.layout.content)
+end