diff --git a/Dockerfile-15 b/Dockerfile-15
index 2bd2038fe5..6e0e08993f 100644
--- a/Dockerfile-15
+++ b/Dockerfile-15
@@ -144,7 +144,8 @@ RUN sed -i \
     -e "s|#unix_socket_directories = '/tmp'|unix_socket_directories = '/var/run/postgresql'|g" \
     -e "s|#session_preload_libraries = ''|session_preload_libraries = 'supautils'|g" \
     -e "s|#include = '/etc/postgresql-custom/supautils.conf'|include = '/etc/postgresql-custom/supautils.conf'|g" \
-    -e "s|#include = '/etc/postgresql-custom/wal-g.conf'|include = '/etc/postgresql-custom/wal-g.conf'|g" /etc/postgresql/postgresql.conf && \
+    -e "s|#include = '/etc/postgresql-custom/wal-g.conf'|include = '/etc/postgresql-custom/wal-g.conf'|g" \
+    -e "s|^summarize_wal = on|#&|g" /etc/postgresql/postgresql.conf && \
     echo "pgsodium.getkey_script= '/usr/lib/postgresql/bin/pgsodium_getkey.sh'" >> /etc/postgresql/postgresql.conf && \
     echo "vault.getkey_script= '/usr/lib/postgresql/bin/pgsodium_getkey.sh'" >> /etc/postgresql/postgresql.conf && \
     chown -R postgres:postgres /etc/postgresql-custom
diff --git a/ansible/files/postgresql_config/postgresql.conf.j2 b/ansible/files/postgresql_config/postgresql.conf.j2
index 154ec13416..9219c14fd0 100644
--- a/ansible/files/postgresql_config/postgresql.conf.j2
+++ b/ansible/files/postgresql_config/postgresql.conf.j2
@@ -227,7 +227,8 @@ wal_level = logical			# minimal, replica, or logical
 #wal_writer_delay = 200ms		# 1-10000 milliseconds
 #wal_writer_flush_after = 1MB		# measured in pages, 0 disables
 #wal_skip_threshold = 2MB
-
+summarize_wal = on		# run WAL summarizer for 17 and up
+#wal_summary_keep_time = '10d'	# when to remove old summary files; 0 = never
 #commit_delay = 0			# range 0-100000, in microseconds
 #commit_siblings = 5			# range 1-1000
 
diff --git a/ansible/tasks/setup-postgres.yml b/ansible/tasks/setup-postgres.yml
index 1bcc0420e4..a630159672 100644
--- a/ansible/tasks/setup-postgres.yml
+++ b/ansible/tasks/setup-postgres.yml
@@ -94,6 +94,13 @@
       loop_control:
         loop_var: 'pg_config_item'
 
+    - name: Disable summarize_wal on PG15 (GUC only exists from PG17)
+      when: psql_version == 'psql_15'
+      ansible.builtin.replace:
+        path: '/etc/postgresql/postgresql.conf'
+        regexp: '^summarize_wal = on'
+        replace: '#summarize_wal = on'
+
     - name: Set data_directory to canonical path on data volume
       ansible.builtin.lineinfile:
         path: '/etc/postgresql/postgresql.conf'
diff --git a/nix/checks.nix b/nix/checks.nix
index 518aac5690..818342e19e 100644
--- a/nix/checks.nix
+++ b/nix/checks.nix
@@ -368,6 +368,7 @@
                   echo "port = ${pgPort}"
                   echo "session_preload_libraries = 'supautils'"
                   echo "dynamic_library_path = '${supautils}/lib:\$libdir'"
+                  ${lib.optionalString (pgpkg.version != "15") ''echo "summarize_wal = on"''}
                 } >> "$PGTAP_CLUSTER"/postgresql.conf
                 echo "host all all 127.0.0.1/32 trust" >> "$PGTAP_CLUSTER/pg_hba.conf"
                 log info "Checking shared_preload_libraries setting:"
diff --git a/nix/tests/expected/z_17_wal_summarize.out b/nix/tests/expected/z_17_wal_summarize.out
new file mode 100644
index 0000000000..80faf63270
--- /dev/null
+++ b/nix/tests/expected/z_17_wal_summarize.out
@@ -0,0 +1,6 @@
+SELECT (SELECT setting FROM pg_settings WHERE name = 'summarize_wal') = 'on' AS summarize_wal_default_ok;
+ summarize_wal_default_ok 
+--------------------------
+ t
+(1 row)
+
diff --git a/nix/tests/sql/z_17_wal_summarize.sql b/nix/tests/sql/z_17_wal_summarize.sql
new file mode 100644
index 0000000000..eec068e11e
--- /dev/null
+++ b/nix/tests/sql/z_17_wal_summarize.sql
@@ -0,0 +1 @@
+SELECT (SELECT setting FROM pg_settings WHERE name = 'summarize_wal') = 'on' AS summarize_wal_default_ok;
diff --git a/nix/tools/run-server.sh.in b/nix/tools/run-server.sh.in
index 6090cab8f0..bc1ca6900c 100644
--- a/nix/tools/run-server.sh.in
+++ b/nix/tools/run-server.sh.in
@@ -246,6 +246,11 @@ session_preload_libraries = 'supautils'" \
 -e "s|include_dir = '/etc/postgresql-custom/conf.d'|include_dir = '$DATDIR/conf.d'|" \
 "$PSQL_CONF_FILE" > "$DATDIR/postgresql.conf"
 
+# summarize_wal is PostgreSQL 17+; PG15 refuses to start on an unknown GUC
+if [ "$VERSION" == "15" ]; then
+    perl -pi -e 's/^summarize_wal = on/#$&/' "$DATDIR/postgresql.conf"
+fi
+
 # Function to configure OrioleDB specific settings
 orioledb_config_items() {
     if [[ "$1" = "orioledb-17" && "$CURRENT_SYSTEM" != "aarch64-darwin" ]]; then