diff --git a/target/rspamd/local.d/antivirus.conf b/target/rspamd/local.d/antivirus.conf
index 2ce4e96f..78c44051 100644
--- a/target/rspamd/local.d/antivirus.conf
+++ b/target/rspamd/local.d/antivirus.conf
@@ -10,4 +10,5 @@ ClamAV {
     scan_mime_parts = false;
     symbol = "CLAM_VIRUS";
     log_clean = true;
+    max_size = 25000000;
 }
diff --git a/target/scripts/startup/setup.d/security/misc.sh b/target/scripts/startup/setup.d/security/misc.sh
index b517d513..be25002a 100644
--- a/target/scripts/startup/setup.d/security/misc.sh
+++ b/target/scripts/startup/setup.d/security/misc.sh
@@ -186,8 +186,18 @@ function __setup__security__clamav
     if [[ ${CLAMAV_MESSAGE_SIZE_LIMIT} != '25M' ]]
     then
       _log 'trace' "Setting ClamAV message scan size limit to '${CLAMAV_MESSAGE_SIZE_LIMIT}'"
-      sedfile -i \
-        "s/^MaxFileSize.*/MaxFileSize ${CLAMAV_MESSAGE_SIZE_LIMIT}/" \
+
+      # do a short sanity checks; ClamAV stops scanning at more that 4GB file size
+      if [[ $(numfmt --from=si "${CLAMAV_MESSAGE_SIZE_LIMIT}") -gt $(numfmt --from=si 4G) ]]
+      then
+        _log 'warn' "You set 'CLAMAV_MESSAGE_SIZE_LIMIT' to a value larger than 4 Gigabyte which ClamAV does not support - you should correct your configuration"
+      fi
+
+      sedfile -i -E \
+        "s|^(MaxFileSize).*|\1 ${CLAMAV_MESSAGE_SIZE_LIMIT}|" \
+        /etc/clamav/clamd.conf
+      sedfile -i -E \
+        "s|^(MaxScanSize).*|\1 ${CLAMAV_MESSAGE_SIZE_LIMIT}|" \
         /etc/clamav/clamd.conf
     fi
   else
diff --git a/target/scripts/startup/setup.d/security/rspamd.sh b/target/scripts/startup/setup.d/security/rspamd.sh
index 4ddb82ca..429a8efb 100644
--- a/target/scripts/startup/setup.d/security/rspamd.sh
+++ b/target/scripts/startup/setup.d/security/rspamd.sh
@@ -164,6 +164,14 @@ function __rspamd__setup_clamav
     sedfile -i -E 's|^(enabled).*|\1 = true;|g' "${RSPAMD_LOCAL_D}/antivirus.conf"
     # Rspamd uses ClamAV's UNIX socket, and to be able to read it, it must be in the same group
     usermod -a -G clamav _rspamd
+
+    if [[ ${CLAMAV_MESSAGE_SIZE_LIMIT} != '25M' ]]
+    then
+      local SIZE_IN_BYTES
+      SIZE_IN_BYTES=$(numfmt --from=si "${CLAMAV_MESSAGE_SIZE_LIMIT}")
+      __rspamd__log 'trace' "Adjusting maximum size for ClamAV to ${SIZE_IN_BYTES} bytes (${CLAMAV_MESSAGE_SIZE_LIMIT})"
+      sedfile -i -E "s|(.*max_size =).*|\1 ${SIZE_IN_BYTES};|" "${RSPAMD_LOCAL_D}/antivirus.conf"
+    fi
   else
     __rspamd__log 'debug' 'Rspamd will not use ClamAV (which has not been enabled)'
   fi
diff --git a/test/tests/parallel/set1/spam_virus/rspamd_full.bats b/test/tests/parallel/set1/spam_virus/rspamd_full.bats
index d0c22a8b..611995c6 100644
--- a/test/tests/parallel/set1/spam_virus/rspamd_full.bats
+++ b/test/tests/parallel/set1/spam_virus/rspamd_full.bats
@@ -20,6 +20,7 @@ function setup_file() {
     --env ENABLE_OPENDMARC=0
     --env ENABLE_POLICYD_SPF=0
     --env ENABLE_POSTGREY=0
+    --env CLAMAV_MESSAGE_SIZE_LIMIT=42M
     --env PERMIT_DOCKER=host
     --env LOG_LEVEL=trace
     --env MOVE_SPAM_TO_JUNK=1
@@ -78,6 +79,7 @@ function teardown_file() { _default_teardown ; }
   run docker logs "${CONTAINER_NAME}"
   assert_success
   assert_line --partial 'Enabling ClamAV integration'
+  assert_line --partial 'Adjusting maximum size for ClamAV to 42000000 bytes (42M)'
   assert_line --partial 'Setting up intelligent learning of spam and ham'
   assert_line --partial 'Enabling greylisting'
   assert_line --partial 'Hfilter (group) module is enabled'
@@ -96,6 +98,11 @@ function teardown_file() { _default_teardown ; }
   _service_log_should_contain_string 'rspamd' 'lua module metric_exporter is disabled in the configuration'
 }
 
+@test 'antivirus maximum size was adjusted' {
+  _run_in_container grep 'max_size = 42000000' /etc/rspamd/local.d/antivirus.conf
+  assert_success
+}
+
 @test 'normal mail passes fine' {
   _service_log_should_contain_string 'rspamd' 'F \(no action\)'
 
diff --git a/test/tests/parallel/set1/spam_virus/rspamd_partly.bats b/test/tests/parallel/set1/spam_virus/rspamd_partly.bats
index 29b7bc0e..bcb2f8d8 100644
--- a/test/tests/parallel/set1/spam_virus/rspamd_partly.bats
+++ b/test/tests/parallel/set1/spam_virus/rspamd_partly.bats
@@ -57,6 +57,11 @@ function teardown_file() { _default_teardown ; }
   assert_line --partial 'Disabling Hfilter (group) module'
 }
 
+@test 'antivirus maximum size was not adjusted unnecessarily' {
+  _run_in_container grep 'max_size = 25000000' /etc/rspamd/local.d/antivirus.conf
+  assert_success
+}
+
 @test 'learning is properly disabled' {
   for FILE in learn-{ham,spam}.{sieve,svbin}
   do