diff --git a/ZertoApiWrapper/Public/Get-ZertoVirtualizationSite.ps1 b/ZertoApiWrapper/Public/Get-ZertoVirtualizationSite.ps1
index af9013f..fa8124d 100644
--- a/ZertoApiWrapper/Public/Get-ZertoVirtualizationSite.ps1
+++ b/ZertoApiWrapper/Public/Get-ZertoVirtualizationSite.ps1
@@ -50,7 +50,7 @@ function Get-ZertoVirtualizationSite {
 
             "devices" {
                 foreach ( $id in $siteIdentifier ) {
-                    if ( $PSBoundParameters.Contains( "hostIdentifier" ) ) {
+                    if ( $PSBoundParameters.ContainsKey( "hostIdentifier" ) ) {
                         $uri = "{0}/{1}/devices?hostIdentifier={2}" -f $baseUri, $siteIdentifier, $hostIdentifier
                     } else {
                         $uri = "{0}/{1}/devices" -f $baseUri, $siteIdentifier
@@ -61,7 +61,7 @@ function Get-ZertoVirtualizationSite {
             }
 
             "hosts" {
-                if ( $PSBoundParameters.Contains( "hostIdentifier" ) ) {
+                if ( $PSBoundParameters.ContainsKey( "hostIdentifier" ) ) {
                     $uri = "{0}/{1}/hosts/{2}" -f $baseUri, $siteIdentifier, $hostIdentifier
                 } else {
                     $uri = "{0}/{1}/hosts" -f $baseUri, $siteIdentifier
diff --git a/ZertoApiWrapper/Public/Get-ZertoVpg.ps1 b/ZertoApiWrapper/Public/Get-ZertoVpg.ps1
index 63d0ae1..a08c33b 100644
--- a/ZertoApiWrapper/Public/Get-ZertoVpg.ps1
+++ b/ZertoApiWrapper/Public/Get-ZertoVpg.ps1
@@ -74,7 +74,7 @@ function Get-ZertoVpg {
 
             "checkpoints" {
                 $filter = $false
-                if ( $PSBoundParameters.Contains("startDate") -or $PSBoundParameters.Contains("endDate") ) {
+                if ( $PSBoundParameters.ContainsKey("startDate") -or $PSBoundParameters.ContainsKey("endDate") ) {
                     $filter = $true
                     $filterTable = @{}
                     foreach ( $key in $PSBoundParameters.Keys ) {