diff --git a/requirements/doc.txt b/requirements/doc.txt
index 313aaea..664d26a 100644
--- a/requirements/doc.txt
+++ b/requirements/doc.txt
@@ -289,19 +289,31 @@ sphinx==7.1.2; python_version < '3.9'
     #   -r requirements/doc.in
     #   pydata-sphinx-theme
     #   sphinx-book-theme
-sphinx-book-theme==1.1.2
+sphinx-book-theme==1.1.2; python_version >= '3.9'
     # via -r requirements/doc.in
-sphinxcontrib-applehelp==1.0.8
+sphinx-book-theme==1.0.1; python_version < '3.9'
+    # via -r requirements/doc.in
+sphinxcontrib-applehelp==1.0.8; python_version >= '3.9'
+    # via sphinx
+sphinxcontrib-applehelp==1.0.4; python_version < '3.9'
+    # via sphinx
+sphinxcontrib-devhelp==1.0.6; python_version >= '3.9'
     # via sphinx
-sphinxcontrib-devhelp==1.0.6
+sphinxcontrib-devhelp==1.0.2; python_version < '3.9'
     # via sphinx
-sphinxcontrib-htmlhelp==2.0.5
+sphinxcontrib-htmlhelp==2.0.5; python_version >= '3.9'
+    # via sphinx
+sphinxcontrib-htmlhelp==2.0.1; python_version < '3.9'
     # via sphinx
 sphinxcontrib-jsmath==1.0.1
     # via sphinx
-sphinxcontrib-qthelp==1.0.7
+sphinxcontrib-qthelp==1.0.7; python_version >= '3.9'
+    # via sphinx
+sphinxcontrib-qthelp==1.0.3; python_version < '3.9'
+    # via sphinx
+sphinxcontrib-serializinghtml==1.1.10; python_version >= '3.9'
     # via sphinx
-sphinxcontrib-serializinghtml==1.1.10
+sphinxcontrib-serializinghtml==1.1.5; python_version < '3.9'
     # via sphinx
 sqlparse==0.4.4
     # via