diff --git a/docs/Project.toml b/docs/Project.toml
index b5a11904..80f4c457 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -4,6 +4,7 @@ DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 Distributions = "31c24e10-a181-5473-b8eb-7969acd0382f"
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
 FillArrays = "1a297f60-69ca-5386-bcde-b61e274b549b"
+Interpolations = "a98d9a8b-a2ab-59e6-89dd-64a1c18fca59"
 KernelDensity = "5ab0869b-81aa-558d-bb23-cbf5423bbe9b"
 NeuralEstimators = "38f6df31-6b4a-4144-b2af-7ace2da57606"
 Plots = "91a5bcdd-55d7-5caf-9e0b-520d859cae80"
@@ -22,6 +23,7 @@ TuringUtilities = {url = "https://github.com/itsdfish/TuringUtilities.jl"}
 Colors = "0.12.0,0.13.0"
 DataFrames = "1.0.0"
 Documenter = "1"
+Interpolations = "0.14.0,0.15.0,0.16.0"
 KernelDensity = "0.6.0"
 Plots = "1.0.0"
 StatsBase = "0.33.0,0.34.0"
diff --git a/docs/make.jl b/docs/make.jl
index 0642632c..6dfb02b9 100644
--- a/docs/make.jl
+++ b/docs/make.jl
@@ -1,7 +1,10 @@
 using Documenter
 using SequentialSamplingModels
 using Turing
+# load all PlotsExt triggers so the extension (and its docstrings) are available
 using Plots
+using Interpolations
+using KernelDensity
 
 makedocs(
     warnonly = true,
diff --git a/src/multi_choice_models/DDM.jl b/src/multi_choice_models/DDM.jl
index 44790b58..bd24c452 100644
--- a/src/multi_choice_models/DDM.jl
+++ b/src/multi_choice_models/DDM.jl
@@ -168,7 +168,7 @@ end
 #########################################
 
 function cdf(d::DDM{T}, choice::Int, rt::Real = 10; ϵ::Real = 1.0e-12) where {T <: Real}
-    @argcheck d.τ < rt
+    rt ≤ d.τ && return zero(float(promote_type(T, typeof(rt))))
     if choice == 1
         (ν, α, z, τ) = params(d)
         return _cdf(DDM(-ν, α, 1 - z, τ), rt; ϵ)