diff --git a/sphinx/environment/collectors/asset.py b/sphinx/environment/collectors/asset.py
index 73dd16869..86a1a3414 100644
--- a/sphinx/environment/collectors/asset.py
+++ b/sphinx/environment/collectors/asset.py
@@ -143,6 +143,12 @@ class DownloadFileCollector(EnvironmentCollector):
 
 
 def setup(app):
-    # type: (Sphinx) -> None
+    # type: (Sphinx) -> Dict
     app.add_env_collector(ImageCollector)
     app.add_env_collector(DownloadFileCollector)
+
+    return {
+        'version': 'builtin',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }
diff --git a/sphinx/environment/collectors/dependencies.py b/sphinx/environment/collectors/dependencies.py
index ebfefe154..fe6ecccb1 100644
--- a/sphinx/environment/collectors/dependencies.py
+++ b/sphinx/environment/collectors/dependencies.py
@@ -18,7 +18,7 @@ from sphinx.environment.collectors import EnvironmentCollector
 
 if False:
     # For type annotation
-    from typing import Set  # NOQA
+    from typing import Dict, Set  # NOQA
     from docutils import nodes  # NOQA
     from sphinx.sphinx import Sphinx  # NOQA
     from sphinx.environment import BuildEnvironment  # NOQA
@@ -56,5 +56,11 @@ class DependenciesCollector(EnvironmentCollector):
 
 
 def setup(app):
-    # type: (Sphinx) -> None
+    # type: (Sphinx) -> Dict
     app.add_env_collector(DependenciesCollector)
+
+    return {
+        'version': 'builtin',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }
diff --git a/sphinx/environment/collectors/indexentries.py b/sphinx/environment/collectors/indexentries.py
index 596c98c09..44aee204c 100644
--- a/sphinx/environment/collectors/indexentries.py
+++ b/sphinx/environment/collectors/indexentries.py
@@ -15,7 +15,7 @@ from sphinx.environment.collectors import EnvironmentCollector
 
 if False:
     # For type annotation
-    from typing import Set  # NOQA
+    from typing import Dict, Set  # NOQA
     from docutils import nodes  # NOQA
     from sphinx.applicatin import Sphinx  # NOQA
     from sphinx.environment import BuildEnvironment  # NOQA
@@ -56,5 +56,11 @@ class IndexEntriesCollector(EnvironmentCollector):
 
 
 def setup(app):
-    # type: (Sphinx) -> None
+    # type: (Sphinx) -> Dict
     app.add_env_collector(IndexEntriesCollector)
+
+    return {
+        'version': 'builtin',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }
diff --git a/sphinx/environment/collectors/metadata.py b/sphinx/environment/collectors/metadata.py
index 4c700b4f2..305a086de 100644
--- a/sphinx/environment/collectors/metadata.py
+++ b/sphinx/environment/collectors/metadata.py
@@ -15,7 +15,7 @@ from sphinx.environment.collectors import EnvironmentCollector
 
 if False:
     # For type annotation
-    from typing import Set  # NOQA
+    from typing import Dict, Set  # NOQA
     from docutils import nodes  # NOQA
     from sphinx.sphinx import Sphinx  # NOQA
     from sphinx.environment import BuildEnvironment  # NOQA
@@ -69,5 +69,11 @@ class MetadataCollector(EnvironmentCollector):
 
 
 def setup(app):
-    # type: (Sphinx) -> None
+    # type: (Sphinx) -> Dict
     app.add_env_collector(MetadataCollector)
+
+    return {
+        'version': 'builtin',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }
diff --git a/sphinx/environment/collectors/title.py b/sphinx/environment/collectors/title.py
index fca394c35..693a1cf32 100644
--- a/sphinx/environment/collectors/title.py
+++ b/sphinx/environment/collectors/title.py
@@ -16,7 +16,7 @@ from sphinx.transforms import SphinxContentsFilter
 
 if False:
     # For type annotation
-    from typing import Set  # NOQA
+    from typing import Dict, Set  # NOQA
     from docutils import nodes  # NOQA
     from sphinx.sphinx import Sphinx  # NOQA
     from sphinx.environment import BuildEnvironment  # NOQA
@@ -62,5 +62,11 @@ class TitleCollector(EnvironmentCollector):
 
 
 def setup(app):
-    # type: (Sphinx) -> None
+    # type: (Sphinx) -> Dict
     app.add_env_collector(TitleCollector)
+
+    return {
+        'version': 'builtin',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }
diff --git a/sphinx/environment/collectors/toctree.py b/sphinx/environment/collectors/toctree.py
index bd3298391..a95e30895 100644
--- a/sphinx/environment/collectors/toctree.py
+++ b/sphinx/environment/collectors/toctree.py
@@ -284,5 +284,11 @@ class TocTreeCollector(EnvironmentCollector):
 
 
 def setup(app):
-    # type: (Sphinx) -> None
+    # type: (Sphinx) -> Dict
     app.add_env_collector(TocTreeCollector)
+
+    return {
+        'version': 'builtin',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }