diff --git a/.github/workflows/plugin-ci-workflow.yml b/.github/workflows/plugin-ci-workflow.yml
index e806000..02b1688 100644
--- a/.github/workflows/plugin-ci-workflow.yml
+++ b/.github/workflows/plugin-ci-workflow.yml
@@ -85,7 +85,7 @@ jobs:
       run: sudo apt-get update
     
     - name: Install System Dependencies
-      run: sudo apt-get install -y apache2 snmp snmpd rrdtool fping libapache2-mod-php${{ matrix.php }}
+      run: sudo apt-get install -y apache2 snmp snmpd rrdtool fping
     
     - name: Start SNMPD Agent and Test
       run: |
diff --git a/lib/WeatherMap.functions.php b/lib/WeatherMap.functions.php
index 90ef0c6..3aa5d5c 100644
--- a/lib/WeatherMap.functions.php
+++ b/lib/WeatherMap.functions.php
@@ -1640,11 +1640,12 @@ function format_number($number, $precision = 2, $trailing_zeroes = 0) {
 		$sign   = -1;
 	}
 
-	$number  = round($number, $precision);
+	$number  = (string) round($number, $precision);
 	$integer = intval($number);
+	$integer_string = (string) $integer;
 
-	if (strlen($integer) < strlen($number)) {
-		$decimal = substr($number, strlen($integer) + 1);
+	if (strlen($integer_string) < strlen($number)) {
+		$decimal = substr($number, strlen($integer_string) + 1);
 	}
 
 	$decimal ??= '';
diff --git a/tests/Unit/FormatNumberTest.php b/tests/Unit/FormatNumberTest.php
new file mode 100644
index 0000000..1e3e4ab
--- /dev/null
+++ b/tests/Unit/FormatNumberTest.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+require_once __DIR__ . '/../bootstrap.php';
+require_once dirname(__DIR__, 2) . '/lib/WeatherMap.functions.php';
+
+describe('format_number', function (): void {
+	it('formats decimal values on PHP 8 without a strlen type error', function (): void {
+		expect(format_number(12.345, 2))->toBe('12.35');
+	});
+
+	it('formats whole numbers without a decimal suffix', function (): void {
+		expect(format_number(12.0, 2))->toBe(12);
+	});
+});