diff --git a/clickhouse/config.xml b/clickhouse/config.xml
index 6127385fb85..1163808f5e1 100644
--- a/clickhouse/config.xml
+++ b/clickhouse/config.xml
@@ -21,7 +21,6 @@
     <error_log remove="remove"/>
     <latency_log remove="remove"/>
 
-    <allow_nullable_key>1</allow_nullable_key>
 
     <profiles>
         <default>
@@ -30,6 +29,7 @@
         </default>
     </profiles>
     <merge_tree>
+        <allow_nullable_key>1</allow_nullable_key>
         <enable_mixed_granularity_parts>1</enable_mixed_granularity_parts>
          <!-- Increase "max_suspicious_broken_parts" in case of errors with Clickhouse like "Suspiciously many broken parts to remove".
               see: https://github.com/getsentry/self-hosted/issues/2832 -->
diff --git a/docker-compose.yml b/docker-compose.yml
index b273dfdfc59..8b2c406b7a2 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -239,7 +239,7 @@ services:
     build:
       context: ./clickhouse
       args:
-        BASE_IMAGE: "altinity/clickhouse-server:25.8.33.10002.altinitystable"
+        BASE_IMAGE: "clickhouse/clickhouse-server:26.8.36.3@sha256:d426d2f612e1e189c90f9a3f8dcd85a03c6851273833817a296bb327e63aa7a7"
     ulimits:
       nofile:
         soft: 262144
diff --git a/install/check-minimum-requirements.sh b/install/check-minimum-requirements.sh
index 91e5116b6d3..c5662507bda 100644
--- a/install/check-minimum-requirements.sh
+++ b/install/check-minimum-requirements.sh
@@ -42,14 +42,14 @@ if [[ "$RAM_AVAILABLE_IN_DOCKER" -lt "$MIN_RAM_HARD" ]]; then
   exit 1
 fi
 
-#SSE4.2 required by Clickhouse (https://clickhouse.yandex/docs/en/operations/requirements/)
-# On KVM, cpuinfo could falsely not report SSE 4.2 support, so skip the check. https://github.com/ClickHouse/ClickHouse/issues/20#issuecomment-226849297
-# This may also happen on other virtualization software such as on VMWare ESXi hosts.
+# ClickHouse requires AVX2. See this: https://github.com/ClickHouse/ClickHouse/issues/40459
+# On KVM, cpuinfo could falsely emit reports, so skip the check. https://github.com/ClickHouse/ClickHouse/issues/20#issuecomment-226849297
+# This may also happen on other virtualization software.
 IS_KVM=$($CONTAINER_ENGINE run --rm busybox grep -c 'Common KVM processor' /proc/cpuinfo || :)
 if [[ ! "$SKIP_SSE42_REQUIREMENTS" -eq 1 && "$IS_KVM" -eq 0 && "$DOCKER_ARCH" = "x86_64" ]]; then
-  SUPPORTS_SSE42=$($CONTAINER_ENGINE run --rm busybox grep -c sse4_2 /proc/cpuinfo || :)
-  if [[ "$SUPPORTS_SSE42" -eq 0 ]]; then
-    echo "FAIL: The CPU your machine is running on does not support the SSE 4.2 instruction set, which is required for one of the services Sentry uses (Clickhouse). See https://github.com/getsentry/self-hosted/issues/340 for more info."
+  SUPPORTS_AVX2=$($CONTAINER_ENGINE run --rm busybox grep -c avx2 /proc/cpuinfo || :)
+  if [[ "$SUPPORTS_AVX2" -eq 0 ]]; then
+    echo "FAIL: The CPU your machine is running on does not support the AVX2 instruction set, which is required for one of the services Sentry uses (Clickhouse). See https://github.com/ClickHouse/ClickHouse/issues/40459 and https://hub.docker.com/r/clickhouse/clickhouse-server#compatibility for more info."
     exit 1
   fi
 fi
diff --git a/install/upgrade-clickhouse.sh b/install/upgrade-clickhouse.sh
index 92e710f3373..36a29c183ed 100644
--- a/install/upgrade-clickhouse.sh
+++ b/install/upgrade-clickhouse.sh
@@ -23,6 +23,13 @@ if $ps_command | grep -q clickhouse; then
     echo "Upgrading clickhouse to 25.8"
     $dcb $build_arg BASE_IMAGE=altinity/clickhouse-server:25.8.33.10002.altinitystable clickhouse
     start_service_and_wait_ready clickhouse
+  elif [[ "$version" == "25.8.33.10002.altinitystable" ]]; then
+    echo "Detected clickhouse version $version"
+    $dc down clickhouse
+
+    echo "Upgrading clickhouse to 26.8"
+    $dcb $build_arg BASE_IMAGE=clickhouse/clickhouse-server:26.8.36.3 clickhouse
+    start_service_and_wait_ready clickhouse
   else
     echo "Detected clickhouse version $version. Skipping upgrades!"
   fi