         // For some reason `swift-corelibs-foundation` failed to open the file as a `Data`.
         let data = try String.init(contentsOfFile: manifestURL.path)
         let manifest = try YAMLDecoder().decode(Manifest.self, from: data)
+        let pkgConfig = manifest.pkgConfig ?? manifest.girName.lowercased()
         
         // Search for location of the generated `.gir` file.
         let optGirPath = try Plan.searchForGir(
             named: manifest.girName, 
-            pkgConfig: [manifest.pkgConfig]
+            pkgConfig: [pkgConfig]
         )
         guard let girPath = optGirPath else {
             throw Error.girNotFound(named: manifest.girName + ".gir" )
         } 
 
         self.girFileToGenerate = girPath
-        self.girFilesToPreload = try Plan.loadPrerequisities(from: girPath, pkgConfig: manifest.pkgConfig, prerequisites: manifest.prerequisites)
-        self.pkgConfigName = manifest.pkgConfig
+        self.girFilesToPreload = try Plan.loadPrerequisities(from: girPath, pkgConfig: pkgConfig, prerequisites: manifest.prerequisites)
+        self.pkgConfigName = pkgConfig
     }
     
     /// Searches for `.gir` file location for given name.

    let girName: String

    /// The name of pkg-config package in which the gir file resides (mainly for the purposes of macOS sandboxing)
    let pkgConfig: String
}

/// Metadata parsed from a `.gir` file. This structure is intended to help in determining the dependency graph of `.gir` files. It represents the contents of `/gir:repository`

        case version
        case girName = "gir-name"
        case pkgConfig = "pkg-config"
        case outputDirectory = "output-directory"
        case alphaNames = "alpha-names"
        case prerequisites
        case postProcess = "post-process"
    }

    /// The version of manifest. It is not utilized now, but I want to keep the property there for future purposes.
    let version: UInt

    /// The name of the gir file associated with the manifest. Extension is NOT expected.
    let girName: String

    /// The name of pkg-config package in which the gir file resides.
    /// If this is `nil`, then the lowercase version of the gir name will be used.
    let pkgConfig: String?

    /// The output directory for the generated files
    let outputDirectory: String?

    /// output alphabetical names
    let alphaNames: Bool?

    /// Optional list of `.gir` prerequisites
    let prerequisites: [Prerequisite]?

    /// Optional list of  files to postprocess
    let postProcess: [String]?
}

/// Description of a `.gir` prerequisite
struct Prerequisite: Codable {
    private enum CodingKeys: String, CodingKey {
        case girName = "gir-name"
