diff --git a/src/functions/assert/String/Should-NotBeString.ps1 b/src/functions/assert/String/Should-NotBeString.ps1
index 1797b9ad8..a9f5b3f3c 100644
--- a/src/functions/assert/String/Should-NotBeString.ps1
+++ b/src/functions/assert/String/Should-NotBeString.ps1
@@ -57,7 +57,7 @@ function Should-NotBeString {
     param (
         [Parameter(Position = 1, ValueFromPipeline = $true)]
         $Actual,
-        [Parameter(Position = 0)]
+        [Parameter(Position = 0, Mandatory)]
         [String]$Expected,
         [String]$Because,
         [switch]$CaseSensitive,
diff --git a/src/functions/assert/Time/Should-BeFasterThan.ps1 b/src/functions/assert/Time/Should-BeFasterThan.ps1
index 450df6629..826f2b9dd 100644
--- a/src/functions/assert/Time/Should-BeFasterThan.ps1
+++ b/src/functions/assert/Time/Should-BeFasterThan.ps1
@@ -47,7 +47,7 @@
     param (
         [Parameter(Position = 1, ValueFromPipeline = $true)]
         $Actual,
-        [Parameter(Position = 0)]
+        [Parameter(Position = 0, Mandatory)]
         $Expected,
         [string] $Because
     )
diff --git a/src/functions/assert/Time/Should-BeSlowerThan.ps1 b/src/functions/assert/Time/Should-BeSlowerThan.ps1
index ef40c0892..2558597f2 100644
--- a/src/functions/assert/Time/Should-BeSlowerThan.ps1
+++ b/src/functions/assert/Time/Should-BeSlowerThan.ps1
@@ -54,7 +54,7 @@
     param (
         [Parameter(Position = 1, ValueFromPipeline = $true)]
         $Actual,
-        [Parameter(Position = 0)]
+        [Parameter(Position = 0, Mandatory)]
         $Expected,
         [string] $Because
     )
diff --git a/tst/functions/assert/String/Should-NotBeString.Tests.ps1 b/tst/functions/assert/String/Should-NotBeString.Tests.ps1
index 1e0d041a6..3211310be 100644
--- a/tst/functions/assert/String/Should-NotBeString.Tests.ps1
+++ b/tst/functions/assert/String/Should-NotBeString.Tests.ps1
@@ -60,5 +60,10 @@ Describe "Should-NotBeString" {
         $err = { Should-NotBeString -Expected "abc" -Actual 1 } | Verify-Throw
         $err.Exception | Verify-Type ([ArgumentException])
     }
+
+    It "Requires Expected" {
+        $err = { "abc" | Should-NotBeString } | Verify-Throw
+        $err.Exception | Verify-Type ([System.Management.Automation.ParameterBindingException])
+    }
 }
 
diff --git a/tst/functions/assert/Time/Should-BeFasterThan.Tests.ps1 b/tst/functions/assert/Time/Should-BeFasterThan.Tests.ps1
index d13b0d5b1..0e8099363 100644
--- a/tst/functions/assert/Time/Should-BeFasterThan.Tests.ps1
+++ b/tst/functions/assert/Time/Should-BeFasterThan.Tests.ps1
@@ -54,4 +54,9 @@ Describe "Should-BeFasterThan" {
         $err = { $Actual | Should-BeFasterThan -Expected $Expected -Because $Because } | Verify-AssertionFailed
         $err.Exception.Message | Verify-Like '*because I said so*'
     }
+
+    It "Requires Expected" {
+        $err = { [timespan]::FromMilliseconds(1) | Should-BeFasterThan } | Verify-Throw
+        $err.Exception | Verify-Type ([System.Management.Automation.ParameterBindingException])
+    }
 }
diff --git a/tst/functions/assert/Time/Should-BeSlowerThan.Tests.ps1 b/tst/functions/assert/Time/Should-BeSlowerThan.Tests.ps1
index 080265d7e..c5458f243 100644
--- a/tst/functions/assert/Time/Should-BeSlowerThan.Tests.ps1
+++ b/tst/functions/assert/Time/Should-BeSlowerThan.Tests.ps1
@@ -31,4 +31,9 @@ Describe "Should-BeSlowerThan" {
         $err = { $Actual | Should-BeSlowerThan -Expected $Expected -Because $Because } | Verify-AssertionFailed
         $err.Exception.Message | Verify-Like '*because I said so*'
     }
+
+    It "Requires Expected" {
+        $err = { [timespan]::FromMilliseconds(1) | Should-BeSlowerThan } | Verify-Throw
+        $err.Exception | Verify-Type ([System.Management.Automation.ParameterBindingException])
+    }
 }