diff --git a/collectors/wsb/Send-WsbBackupStatus.ps1 b/collectors/wsb/Send-WsbBackupStatus.ps1
index 3b03349..89f87d3 100644
--- a/collectors/wsb/Send-WsbBackupStatus.ps1
+++ b/collectors/wsb/Send-WsbBackupStatus.ps1
@@ -44,8 +44,9 @@ $DataDir = Split-Path -Parent $ConfigPath
 $LogPath = Join-Path $DataDir 'wsb-collector.log'
 $StatePath = Join-Path $DataDir 'wsb-collector.state.json'
 $MaxLogBytes = 5MB
-# Covers 30 days at several backups a day
-$MaxPreviousJobs = 200
+# Get-WBJob -Previous accepts at most 100. That covers a 30-day backfill at up to 3 backups a day;
+# servers backing up more often only get their latest 100 runs backfilled.
+$MaxPreviousJobs = 100
 $Invariant = [Globalization.CultureInfo]::InvariantCulture
 
 # ---------- Helpers ----------
diff --git a/collectors/wsb/tests/MockWsb.ps1 b/collectors/wsb/tests/MockWsb.ps1
index 8689f64..cc18374 100644
--- a/collectors/wsb/tests/MockWsb.ps1
+++ b/collectors/wsb/tests/MockWsb.ps1
@@ -92,7 +92,8 @@ $global:MockWsbSummary = [pscustomobject]@{
     CurrentOperationStatus   = $(if ($WithRunningJob) { 'BackupInProgress' } else { 'NoOperationInProgress' })
 }
 
-function Get-WBJob { param([int]$Previous) if ($PSBoundParameters.ContainsKey('Previous')) { $global:MockWsbPrevious } else { $global:MockWsbRunning } }
+# Same limit as the real cmdlet
+function Get-WBJob { param([ValidateRange(1, 100)][int]$Previous) if ($PSBoundParameters.ContainsKey('Previous')) { $global:MockWsbPrevious } else { $global:MockWsbRunning } }
 function Get-WBSummary { $global:MockWsbSummary }
 function Get-WBPolicy { [pscustomobject]@{ PolicyName = 'Scheduled' } }
 function Get-WBSchedule { param($Policy) @($global:MockWsbSummary.NextBackupTime) }