diff --git a/CHANGELOG.md b/CHANGELOG.md
index a9d083e4..7c60422b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - The minimum supported julia version is increased to 1.6. ([#328])
+- Test for undocumented names is now activated by default ([#368])
 
 ## Version [v0.8.14] - 2025-08-04
 
diff --git a/src/Aqua.jl b/src/Aqua.jl
index acc33a39..b630197e 100644
--- a/src/Aqua.jl
+++ b/src/Aqua.jl
@@ -46,7 +46,7 @@ passed to `\$x` to specify the keyword arguments for `test_\$x`.
 - `deps_compat = true`
 - `piracies = true`
 - `persistent_tasks = true`
-- `undocumented_names = false`
+- `undocumented_names = true`
 """
 function test_all(
     testtarget::Module;
@@ -58,7 +58,7 @@ function test_all(
     deps_compat = true,
     piracies = true,
     persistent_tasks = true,
-    undocumented_names = false,
+    undocumented_names = true,
 )
     if ambiguities !== false
         @testset "Method ambiguity" begin
diff --git a/src/exports.jl b/src/exports.jl
index 80c7bebf..61b8cbcd 100644
--- a/src/exports.jl
+++ b/src/exports.jl
@@ -7,15 +7,15 @@ function isbindingresolved(m::Module, s::Symbol)
     end
 end
 
-function walkmodules(f, x::Module)
+function walkmodules(f, x::Module; all::Bool = true)
     f(x)
-    for n in names(x; all = true)
+    for n in names(x; all)
         # `isdefined` and `getproperty` can trigger deprecation warnings
         if isbindingresolved(x, n) && !Base.isdeprecated(x, n)
             isdefined(x, n) || continue
             y = getproperty(x, n)
             if y isa Module && y !== x && parentmodule(y) === x
-                walkmodules(f, y)
+                walkmodules(f, y; all)
             end
         end
     end
diff --git a/src/undocumented_names.jl b/src/undocumented_names.jl
index 40e749da..e4eb1a0e 100644
--- a/src/undocumented_names.jl
+++ b/src/undocumented_names.jl
@@ -22,7 +22,7 @@ function test_undocumented_names(m::Module; broken::Bool = false)
     @static if VERSION >= v"1.11"
         # exclude the module name itself because it has the README as auto-generated docstring (https://github.com/JuliaLang/julia/pull/39093)
         undocumented_names = Symbol[]
-        walkmodules(m) do x
+        walkmodules(m; all=false) do x  # we don't care about undocumented names in private submodules
             append!(undocumented_names, Docs.undocumented_names(x))
         end
         undocumented_names = filter(n -> n != nameof(m), undocumented_names)
diff --git a/test/pkgs/PkgWithUndocumentedNamesInSubmodule.jl b/test/pkgs/PkgWithUndocumentedNamesInSubmodule.jl
index deddc03b..c00fe1c7 100644
--- a/test/pkgs/PkgWithUndocumentedNamesInSubmodule.jl
+++ b/test/pkgs/PkgWithUndocumentedNamesInSubmodule.jl
@@ -11,4 +11,6 @@ struct UndocumentedStruct end
 
 end
 
+export SubModule
+
 end  # module