diff --git a/Cargo.lock b/Cargo.lock
index 955f96d6903..328a2204306 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,7 +1,5 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
-
 [[package]]
 name = "addr2line"
 version = "0.14.0"
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 9317c89625d..22a1eb63702 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -397,6 +397,7 @@ impl<'a> Builder<'a> {
                 test::Crate,
                 test::CrateLibrustc,
                 test::CrateRustdoc,
+                test::CrateRustdocJsonTypes,
                 test::Linkcheck,
                 test::TierCheck,
                 test::Cargotest,
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index c0cd24dd81f..03ae684e23f 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -1922,6 +1922,77 @@ impl Step for CrateRustdoc {
     }
 }
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct CrateRustdocJsonTypes {
+    host: TargetSelection,
+    test_kind: TestKind,
+}
+
+impl Step for CrateRustdocJsonTypes {
+    type Output = ();
+    const DEFAULT: bool = true;
+    const ONLY_HOSTS: bool = true;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.path("src/rustdoc-json-types")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        let builder = run.builder;
+
+        let test_kind = builder.kind.into();
+
+        builder.ensure(CrateRustdocJsonTypes { host: run.target, test_kind });
+    }
+
+    fn run(self, builder: &Builder<'_>) {
+        let test_kind = self.test_kind;
+        let target = self.host;
+
+        // Use the previous stage compiler to reuse the artifacts that are
+        // created when running compiletest for src/test/rustdoc. If this used
+        // `compiler`, then it would cause rustdoc to be built *again*, which
+        // isn't really necessary.
+        let compiler = builder.compiler_for(builder.top_stage, target, target);
+        builder.ensure(compile::Rustc { compiler, target });
+
+        let mut cargo = tool::prepare_tool_cargo(
+            builder,
+            compiler,
+            Mode::ToolRustc,
+            target,
+            test_kind.subcommand(),
+            "src/rustdoc-json-types",
+            SourceType::InTree,
+            &[],
+        );
+        if test_kind.subcommand() == "test" && !builder.fail_fast {
+            cargo.arg("--no-fail-fast");
+        }
+
+        cargo.arg("-p").arg("rustdoc-json-types");
+
+        cargo.arg("--");
+        cargo.args(&builder.config.cmd.test_args());
+
+        if self.host.contains("musl") {
+            cargo.arg("'-Ctarget-feature=-crt-static'");
+        }
+
+        if !builder.config.verbose_tests {
+            cargo.arg("--quiet");
+        }
+
+        builder.info(&format!(
+            "{} rustdoc-json-types stage{} ({} -> {})",
+            test_kind, compiler.stage, &compiler.host, target
+        ));
+        let _time = util::timeit(&builder);
+
+        try_run(builder, &mut cargo.into());
+    }
+}
+
 /// Some test suites are run inside emulators or on remote devices, and most
 /// of our test binaries are linked dynamically which means we need to ship
 /// the standard library and such to the emulator ahead of time. This step
diff --git a/src/librustdoc/json/mod.rs b/src/librustdoc/json/mod.rs
index 2302dfdc80a..8b0c049c05b 100644
--- a/src/librustdoc/json/mod.rs
+++ b/src/librustdoc/json/mod.rs
@@ -242,7 +242,7 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
                     )
                 })
                 .collect(),
-            format_version: 5,
+            format_version: 4,
         };
         let mut p = self.out_path.clone();
         p.push(output.index.get(&output.root).unwrap().name.clone().unwrap());