diff --git a/README.md b/README.md
index 46b8a84..0ed46b8 100644
--- a/README.md
+++ b/README.md
@@ -109,6 +109,7 @@ There are other environment variables if you want to customize various things in
 | `INTERFACE: <NIC>`<br/> *Advanced/Optional* | The default works fine with our basic example docker run commands.  If you're trying to use DHCP with `--net host` mode then you may have to customize this or DNSMASQ_LISTENING.
 | `DNSMASQ_LISTENING: <local\|all\|single>`<br/> *Advanced/Optional* | `local` listens on all local subnets, `all` permits listening on internet origin subnets in addition to local, `single` listens only on the interface specified.
 | `WEB_PORT: <PORT>`<br/> *Advanced/Optional* | **This will break the 'webpage blocked' functionality of Pi-hole** however it may help advanced setups like those running synology or `--net=host` docker argument.  This guide explains how to restore webpage blocked functionality using a linux router DNAT rule: [Alternative Synology installation method](https://discourse.pi-hole.net/t/alternative-synology-installation-method/5454?u=diginc)
+| `CUSTOM_CACHE_SIZE: <size>`<br/> *Advanced/Optional: Default: '10000'* | Set the cache size for dnsmasq. Useful for increasing the default cache size or to set it to 0. Note that when `DNSSEC` is "true", then this setting is ignored.
 | `DNSMASQ_USER: <pihole\|root>`<br/> *Experimental Default: root* | Allows running FTLDNS as non-root.
 | `TEMPERATUREUNIT`: <c\|k\|f><br/>*Optional Default: c* | Set preferred temperature unit to `c`: Celsius, `k`: Kelvin, or `f` Fahrenheit units.
 | `WEBUIBOXEDLAYOUT: <boxed\|traditional>`<br/>*Optional Default: boxed* | Use boxed layout (helpful when working on large screens)
diff --git a/bash_functions.sh b/bash_functions.sh
index ca4c646..1b4a070 100644
--- a/bash_functions.sh
+++ b/bash_functions.sh
@@ -103,6 +103,7 @@ setup_dnsmasq() {
     setup_dnsmasq_interface "$interface"
     setup_dnsmasq_listening_behaviour "$dnsmasq_listening_behaviour"
     setup_dnsmasq_user "${DNSMASQ_USER}"
+    setup_cache_size "${CUSTOM_CACHE_SIZE}"
     ProcessDNSSettings
 }
 
@@ -157,6 +158,32 @@ setup_dnsmasq_hostnames() {
     fi
 }
 
+setup_cache_size() {
+    local warning="WARNING: CUSTOM_CACHE_SIZE not used"
+    local dnsmasq_pihole_01_location="/etc/dnsmasq.d/01-pihole.conf"
+    # Quietly exit early for empty or default
+    if [[ -z "${1}" || "${1}" == '10000' ]] ; then return ; fi
+
+    if [[ "${DNSSEC}" == "true" ]] ; then
+        echo "$warning - Cannot change cache size if DNSSEC is enabled"
+        return
+    fi
+
+    if ! echo $1 | grep -q '^[0-9]*$' ; then
+        echo "$warning - $1 is not an integer"
+        return
+    fi
+
+    local -i custom_cache_size="$1"
+    if (( $custom_cache_size < 0 )); then
+        echo "$warning - $custom_cache_size is not a positive integer or zero"
+        return
+    fi
+    echo "Custom CUSTOM_CACHE_SIZE set to $custom_cache_size"
+
+    sed -i "s/^cache-size=\s*[0-9]*/cache-size=$custom_cache_size/" ${dnsmasq_pihole_01_location}
+}
+
 setup_lighttpd_bind() {
     local serverip="$1"
     # if using '--net=host' only bind lighttpd on $ServerIP and localhost
diff --git a/start.sh b/start.sh
index 91f2393..5cac513 100755
--- a/start.sh
+++ b/start.sh
@@ -38,6 +38,7 @@ export DHCP_LEASETIME
 export PIHOLE_DOMAIN
 export DHCP_IPv6
 export DHCP_rapid_commit
+export CUSTOM_CACHE_SIZE
 
 export adlistFile='/etc/pihole/adlists.list'
 
diff --git a/test/test_bash_functions.py b/test/test_bash_functions.py
index 8773d41..2402fed 100644
--- a/test/test_bash_functions.py
+++ b/test/test_bash_functions.py
@@ -48,6 +48,39 @@ def test_bad_input_to_WEB_PORT(Docker, test_args, expected_error):
     assert expected_error in function.stdout
 
 
+@pytest.mark.parametrize('test_args,cache_size', [('-e CUSTOM_CACHE_SIZE="0"', '0'), ('-e CUSTOM_CACHE_SIZE="20000"', '20000')])
+def test_overrides_default_CUSTOM_CACHE_SIZE(Docker, Slow, test_args, cache_size):
+    ''' Changes the cache_size setting to increase or decrease the cache size for dnsmasq'''
+    CONFIG_LINE = r'cache-size\s*=\s*{}'.format(cache_size)
+    DNSMASQ_CONFIG = '/etc/dnsmasq.d/01-pihole.conf'
+
+    function = Docker.run('echo ${CUSTOM_CACHE_SIZE};. ./bash_functions.sh; echo ${CUSTOM_CACHE_SIZE}; eval `grep setup_dnsmasq /start.sh`')
+    assert "Custom CUSTOM_CACHE_SIZE set to {}".format(cache_size) in function.stdout
+    Slow(lambda: re.search(CONFIG_LINE, Docker.run('cat {}'.format(DNSMASQ_CONFIG)).stdout) != None)
+
+
+@pytest.mark.parametrize('test_args', [
+    '-e CUSTOM_CACHE_SIZE="-1"',
+    '-e CUSTOM_CACHE_SIZE="1,000"',
+])
+def test_bad_input_to_CUSTOM_CACHE_SIZE(Docker, Slow, test_args):
+    CONFIG_LINE = r'cache-size\s*=\s*10000'
+    DNSMASQ_CONFIG = '/etc/dnsmasq.d/01-pihole.conf'
+
+    Docker.run('. ./bash_functions.sh; eval `grep setup_dnsmasq /start.sh`')
+    Slow(lambda: re.search(CONFIG_LINE, Docker.run('cat {}'.format(DNSMASQ_CONFIG)).stdout) != None)
+
+@pytest.mark.parametrize('test_args', [
+    '-e DNSSEC="true" -e CUSTOM_CACHE_SIZE="0"',
+])
+def test_dnssec_enabled_with_CUSTOM_CACHE_SIZE(Docker, Slow, test_args):
+    CONFIG_LINE = r'cache-size\s*=\s*10000'
+    DNSMASQ_CONFIG = '/etc/dnsmasq.d/01-pihole.conf'
+
+    Docker.run('. ./bash_functions.sh; eval `grep setup_dnsmasq /start.sh`')
+    Slow(lambda: re.search(CONFIG_LINE, Docker.run('cat {}'.format(DNSMASQ_CONFIG)).stdout) != None)
+
+
 # DNS Environment Variable behavior in combinations of modified pihole LTE settings
 @pytest.mark.skip('broke, needs investigation in v5.0 beta')
 @pytest.mark.parametrize('args_env, expected_stdout, dns1, dns2', [