diff --git a/.readthedocs.requirements.txt b/.readthedocs.requirements.txt
index 1f028de414..e69de29bb2 100644
--- a/.readthedocs.requirements.txt
+++ b/.readthedocs.requirements.txt
@@ -1 +0,0 @@
-sphinx==4.4.0
diff --git a/.readthedocs.yml b/.readthedocs.yml
index e66d3da1b1..bf71c46b78 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -5,7 +5,7 @@
 version: 2
 
 build:
-  os: ubuntu-20.04
+  os: ubuntu-22.04
   tools:
     python: "3"
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1b435a8292..2e0ab8b156 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -196,7 +196,7 @@ endif()
 
 # set up versioning.
 set(DF_VERSION "0.47.05")
-set(DFHACK_RELEASE "r8")
+set(DFHACK_RELEASE "r9")
 set(DFHACK_PRERELEASE FALSE)
 
 set(DFHACK_VERSION "${DF_VERSION}-${DFHACK_RELEASE}")
@@ -419,6 +419,9 @@ include_directories(depends/tthread)
 include_directories(${ZLIB_INCLUDE_DIRS})
 include_directories(depends/clsocket/src)
 include_directories(depends/xlsxio/include)
+# CMake 4 removed support for policy versions older than 3.5. Keep the
+# bundled third-party projects buildable without modifying their submodules.
+set(CMAKE_POLICY_VERSION_MINIMUM 3.5)
 add_subdirectory(depends)
 
 # Testing with CTest
diff --git a/docs/changelog.txt b/docs/changelog.txt
index 2c000262be..c8472e03df 100644
--- a/docs/changelog.txt
+++ b/docs/changelog.txt
@@ -55,6 +55,11 @@ changelog.txt uses a syntax similar to RST, with a few special sequences:
 ## Removed
 - ``fix-job-postings`` from the `workflow` plugin is now obsolete since affected savegames can no longer be loaded
 
+# 0.47.05-r9
+
+## Internals
+- Fixed building with newer versions of CMake and GCC
+
 # 0.47.05-r8
 
 ## New Plugins
diff --git a/plugins/remotefortressreader/remotefortressreader.cpp b/plugins/remotefortressreader/remotefortressreader.cpp
index 643e92b210..4ee0c36d61 100644
--- a/plugins/remotefortressreader/remotefortressreader.cpp
+++ b/plugins/remotefortressreader/remotefortressreader.cpp
@@ -1693,9 +1693,6 @@ static command_result GetUnitListInside(color_ostream &stream, const BlockReques
                 continue;
         }
 
-        using df::global::cur_year;
-        using df::global::cur_year_tick;
-
         send_unit->set_age(Units::getAge(unit, false));
 
         ConvertDfColor(Units::getProfessionColor(unit), send_unit->mutable_profession_color());
diff --git a/plugins/search.cpp b/plugins/search.cpp
index 9ecae6460b..2990aba3b6 100644
--- a/plugins/search.cpp
+++ b/plugins/search.cpp
@@ -809,6 +809,8 @@ class pets_search : public pets_search_base
         return get_unit_description(element.unit);
     }
 
+    using pets_search_base::should_check_input;
+
     bool should_check_input()
     {
         return viewscreen->mode == T_mode::List;