diff --git a/docs/Project.toml b/docs/Project.toml
index c2785383adf..ce87d157203 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -2,4 +2,4 @@
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
 
 [compat]
-Documenter = "~0.20"
+Documenter = "~0.21"
diff --git a/docs/make.jl b/docs/make.jl
index dc68e8c0382..82fef70ddc9 100644
--- a/docs/make.jl
+++ b/docs/make.jl
@@ -10,7 +10,7 @@ using Documenter, JuMP
 makedocs(
     sitename = "JuMP",
     # See https://github.com/JuliaDocs/Documenter.jl/issues/868
-    html_prettyurls = get(ENV, "CI", nothing) == "true",
+    format = Documenter.HTML(prettyurls = get(ENV, "CI", nothing) == "true"),
     # See https://github.com/JuliaOpt/JuMP.jl/issues/1576
     strict = true,
     authors = "Miles Lubin, Iain Dunning, and Joey Huchette",