diff --git a/cache/framework_cache.psm1 b/cache/framework_cache.psm1
index 4bb99511..aec9f15d 100644
--- a/cache/framework_cache.psm1
+++ b/cache/framework_cache.psm1
@@ -1,4 +1,4 @@
-<#
+<#
     ### Note ###
 
     This file is shipping plain with Icinga for Windows for each version.
diff --git a/doc/100-General/10-Changelog.md b/doc/100-General/10-Changelog.md
index 8a00bd68..bc4da65c 100644
--- a/doc/100-General/10-Changelog.md
+++ b/doc/100-General/10-Changelog.md
@@ -17,6 +17,7 @@ Released closed milestones can be found on [GitHub](https://github.com/Icinga/ic
 * [#476](https://github.com/Icinga/icinga-powershell-framework/pull/476) Fixes exception `You cannot call a method on va null-valued expression` during installation in case no background daemon is configured
 * [#482](https://github.com/Icinga/icinga-powershell-framework/pull/482) Fixes encoding problems with special chars or German umlauts during plugin execution and unescaped whitespace in plugin argument strings like `Icinga for Windows`, which was previously wrongly rended as `Icinga` for example
 * [#489](https://github.com/Icinga/icinga-powershell-framework/issues/489) Fixes error message `This argument does not support the % unit` in case a `BaseValue` is set, but the actual value is `0`
+* [#503](https://github.com/Icinga/icinga-powershell-framework/issues/503) Fixes wrong conversion of values for `Convert-IcingaPluginThresholds`, which did not properly handle string values containing certain units inside the string itself
 * [#505](https://github.com/Icinga/icinga-powershell-framework/issues/505) Fixes certificate generation and host registration, in case a custom hostname was set during usage of `Install-Icinga` automation
 * [#529](https://github.com/Icinga/icinga-powershell-framework/pull/529) Fixes package manifest reader for Icinga for Windows components on Windows 2012 R2 and older
 * [#523](https://github.com/Icinga/icinga-powershell-framework/pull/523) Fixes errors on encapsulated PowerShell calls for missing Cmdlets `Write-IcingaConsoleError` and `Optimize-IcingaForWindowsMemory`
diff --git a/lib/core/tools/Convert-Bytes.psm1 b/lib/core/tools/Convert-Bytes.psm1
index c4228b3d..6c648717 100644
--- a/lib/core/tools/Convert-Bytes.psm1
+++ b/lib/core/tools/Convert-Bytes.psm1
@@ -8,11 +8,11 @@ function Convert-Bytes()
     # Ensure we always use proper formatting of values
     $Value = $Value.Replace(',', '.');
 
-    If (($Value -Match "(^[\d\.]*) ?(B|KB|MB|GB|TB|PT|KiB|MiB|GiB|TiB|PiB)") -eq $FALSE) {
+    If (($Value -Match "(^-?[0-9].*)+((\.|\,)+[0-9])?(B|KB|MB|GB|TB|PT|KiB|MiB|GiB|TiB|PiB)") -eq $FALSE) {
         $Value = [string]::Format('{0}B', $Value);
     }
 
-    If (($Value -Match "(^[\d\.]*) ?(B|KB|MB|GB|TB|PT|KiB|MiB|GiB|TiB|PiB)")) {
+    If (($Value -Match "(^-?[0-9].*)+((\.|\,)+[0-9])?(B|KB|MB|GB|TB|PT|KiB|MiB|GiB|TiB|PiB)")) {
         [single]$CurrentValue = $Matches[1];
         [string]$CurrentUnit = $Matches[2];
 
diff --git a/lib/core/tools/Convert-IcingaPluginThresholds.psm1 b/lib/core/tools/Convert-IcingaPluginThresholds.psm1
index 8987b39a..09e6265e 100644
--- a/lib/core/tools/Convert-IcingaPluginThresholds.psm1
+++ b/lib/core/tools/Convert-IcingaPluginThresholds.psm1
@@ -134,14 +134,14 @@ function Convert-IcingaPluginThresholds()
             $ThresholdValue = $ThresholdValue.Substring(1, $ThresholdValue.Length - 1);
         }
 
-        If (($ThresholdValue -Match "(^[\d\.]*) ?(B|KB|MB|GB|TB|PT|KiB|MiB|GiB|TiB|PiB)")) {
+        If (($ThresholdValue -Match "(^-?[0-9].*)+((\.|\,)+[0-9])?(B|KB|MB|GB|TB|PT|KiB|MiB|GiB|TiB|PiB)")) {
             $WorkUnit = 'B';
             if ([string]::IsNullOrEmpty($RetValue.Unit) -eq $FALSE -And $RetValue.Unit -ne $WorkUnit) {
                 Exit-IcingaThrowException -ExceptionType 'Input' -ExceptionThrown $IcingaExceptions.Inputs.MultipleUnitUsage -Force;
             }
             $Value         = (Convert-Bytes -Value $ThresholdValue -Unit $WorkUnit).Value;
             $RetValue.Unit = $WorkUnit;
-        } elseif (($ThresholdValue -Match "(^[\d\.]*) ?(ms|s|m|h|d|w|M|y)")) {
+        } elseif (($ThresholdValue -Match "(^-?[0-9].*)+((\.|\,)+[0-9])?(ms|s|m|h|d|w|M|y)")) {
             $WorkUnit = 's';
             if ([string]::IsNullOrEmpty($RetValue.Unit) -eq $FALSE -And $RetValue.Unit -ne $WorkUnit) {
                 Exit-IcingaThrowException -ExceptionType 'Input' -ExceptionThrown $IcingaExceptions.Inputs.MultipleUnitUsage -Force;