diff --git a/src/deprecated.jl b/src/deprecated.jl
new file mode 100644
index 0000000..929e55e
--- /dev/null
+++ b/src/deprecated.jl
@@ -0,0 +1,5 @@
+Base.@deprecate propagate(maxsteps, jd0, tspan, ::Val{true}; dynamics = NBP_pN_A_J23E_J23M_J2S_threads!,
+                   nast = 343, order = order, abstol = abstol, parse_eqs = true) propagate(maxsteps, jd0, tspan; dynamics = NBP_pN_A_J23E_J23M_J2S_threads!,
+                   nast = 343, order = order, abstol = abstol, parse_eqs = true)
+Base.@deprecate propagate(maxsteps, jd0, tspan, ::Val{false}; dynamics = NBP_pN_A_J23E_J23M_J2S_threads!,
+                   nast = 343, order = order, abstol = abstol, parse_eqs = true) error("PlanetaryEphemeris.propagate always returns dense output.")