When my build runs, the Pack step fails with the following in the log:

[17:15:12][pack] Starting NuGet.exe 2.8.60318.667 from C:\Program Files (x86)\JetBrains\TeamCity\buildAgent\tools\NuGet.CommandLine.DEFAULT.nupkg\tools\NuGet.exe
[17:15:12][pack] Attempting to build package from 'ComForms.nuspec'.
[17:15:12][pack] Invalid assembly reference 'Ionic.Zip.dll'. Ensure that a file named 'Ionic.Zip.dll' exists in the lib directory.

MSBuild finds the assembly reference without a problem, so I know the file is in the output directory, but how can I refence the assembly such that the Pack step can find it?

Here is my Nuspec file:

<?xml version="1.0"?>
<package xmlns="http://schemas.microsoft.com/packaging/2011/08/nuspec.xsd">
<id>ComForms</id>
<version>1.0.4.5054</version>
<title>ComForms</title>
<authors>Perennial Software</authors>
<owners>Perennial Software</owners>