diff --git a/utils/build.ps1 b/utils/build.ps1
index bbeb1d2826d47..adb0f4867379c 100644
--- a/utils/build.ps1
+++ b/utils/build.ps1
@@ -557,6 +557,7 @@ function Invoke-Program() {
     [string] $Executable,
     [switch] $OutNull = $false,
     [string] $OutFile = "",
+    [string] $ErrorFile = "",
     [Parameter(Position = 1, ValueFromRemainingArguments)]
     [string[]] $Args
   )
@@ -585,16 +586,23 @@ function Invoke-Program() {
 
     if ($OutNull) {
       $OutputLine += " > nul"
-    } elseif ("" -ne $OutFile) {
+    } elseif ($OutFile) {
       $OutputLine += " > `"$OutFile`""
     }
+    if ($ErrorFile) {
+      $OutputLine += " 2> `"$ErrorFile`""
+    }
 
     Write-Output $OutputLine
   } else {
     if ($OutNull) {
       & $Executable @Args | Out-Null
-    } elseif ("" -ne $OutFile) {
-      & $Executable @Args | Out-File -Encoding UTF8 $OutFile
+    } elseif ($OutFile -and $ErrorFile) {
+      & $Executable @Args > $OutFile 2> $ErrorFile
+    } elseif ($OutFile) {
+      & $Executable @Args > $OutFile
+    } elseif ($ErrorFile) {
+      & $Executable @Args 2> $ErrorFile
     } else {
       & $Executable @Args
     }
@@ -1811,9 +1819,17 @@ function Build-mimalloc() {
   foreach ($Tool in $Tools) {
     $Binary = [IO.Path]::Combine($Arch.ToolchainInstallRoot, "usr", "bin", $Tool)
     # Binary-patch in place
-    Start-Process -Wait -WindowStyle Hidden -FilePath "$SourceCache\mimalloc\bin\minject$BuildSuffix" -ArgumentList @("-f", "-i", "-v", "$Binary")
+    Invoke-Program "$SourceCache\mimalloc\bin\minject$BuildSuffix" "-f" "-i" "-v" "$Binary"
     # Log the import table
-    Start-Process -Wait -WindowStyle Hidden -FilePath "$SourceCache\mimalloc\bin\minject$BuildSuffix" -ArgumentList @("-l", "$Binary")
+    $LogFile = "$BinaryCache\$($Arch.LLVMTarget)\mimalloc\minject-log-$Tool.txt"
+    $ErrorFile = "$BinaryCache\$($Arch.LLVMTarget)\mimalloc\minject-log-$Tool-error.txt"
+    Invoke-Program "$SourceCache\mimalloc\bin\minject$BuildSuffix" "-l" "$Binary" -OutFile $LogFile -ErrorFile $ErrorFile
+    # Verify patching
+    $Found = Select-String -Path $LogFile -Pattern "mimalloc"
+    if (-not $Found) {
+      Get-Content $ErrorFile
+      throw "Failed to patch mimalloc for $Tool"
+    }
   }
 }