diff --git a/Docs/ProjectSpec.md b/Docs/ProjectSpec.md
index 08cc8200..f0fd6687 100644
--- a/Docs/ProjectSpec.md
+++ b/Docs/ProjectSpec.md
@@ -218,6 +218,7 @@ A source can be provided via a string (the path) or an object of the form:
 	- `file`: a file reference with a parent group will be created (Default for files or directories with extensions)
 	- `group`: a group with all it's containing files. (Default for directories without extensions)
 	- `folder`: a folder reference.
+  - ⚪️ **optional**: `Bool` - Disable missing path check. Defaults to false.
 
 
 ```yaml
diff --git a/Sources/ProjectSpec/SpecValidation.swift b/Sources/ProjectSpec/SpecValidation.swift
index 471557a7..cbcbd842 100644
--- a/Sources/ProjectSpec/SpecValidation.swift
+++ b/Sources/ProjectSpec/SpecValidation.swift
@@ -63,7 +63,7 @@ extension ProjectSpec {
 
             for source in target.sources {
                 let sourcePath = basePath + source.path
-                if !sourcePath.exists {
+                if !source.optional && !sourcePath.exists {
                     errors.append(.invalidTargetSource(target: target.name, source: sourcePath.string))
                 }
             }
diff --git a/Sources/ProjectSpec/TargetSource.swift b/Sources/ProjectSpec/TargetSource.swift
index 8807b80f..f1e427a5 100644
--- a/Sources/ProjectSpec/TargetSource.swift
+++ b/Sources/ProjectSpec/TargetSource.swift
@@ -9,6 +9,7 @@ public struct TargetSource {
     public var compilerFlags: [String]
     public var excludes: [String]
     public var type: SourceType?
+    public var optional: Bool
 
     public enum SourceType: String {
         case group
@@ -16,12 +17,13 @@ public struct TargetSource {
         case folder
     }
 
-    public init(path: String, name: String? = nil, compilerFlags: [String] = [], excludes: [String] = [], type: SourceType? = nil) {
+    public init(path: String, name: String? = nil, compilerFlags: [String] = [], excludes: [String] = [], type: SourceType? = nil, optional: Bool = false) {
         self.path = path
         self.name = name
         self.compilerFlags = compilerFlags
         self.excludes = excludes
         self.type = type
+        self.optional = optional
     }
 }
 
@@ -53,6 +55,7 @@ extension TargetSource: JSONObjectConvertible {
 
         excludes = jsonDictionary.json(atKeyPath: "excludes") ?? []
         type = jsonDictionary.json(atKeyPath: "type")
+        optional = jsonDictionary.json(atKeyPath: "optional") ?? false
     }
 }
 
@@ -64,5 +67,6 @@ extension TargetSource: Equatable {
             && lhs.compilerFlags == rhs.compilerFlags
             && lhs.excludes == rhs.excludes
             && lhs.type == rhs.type
+            && lhs.optional == rhs.optional
     }
 }
diff --git a/Tests/XcodeGenKitTests/ProjectSpecTests.swift b/Tests/XcodeGenKitTests/ProjectSpecTests.swift
index d8393335..92267b7a 100644
--- a/Tests/XcodeGenKitTests/ProjectSpecTests.swift
+++ b/Tests/XcodeGenKitTests/ProjectSpecTests.swift
@@ -101,6 +101,16 @@ func projectSpecTests() {
                 try expectValidationError(spec, .invalidSchemeConfig(scheme: "scheme1", config: "debugInvalid"))
                 try expectValidationError(spec, .invalidSchemeConfig(scheme: "scheme1", config: "releaseInvalid"))
             }
+
+            $0.it("allows missing optional file") {
+                var spec = baseSpec
+                spec.targets = [Target(name: "target1",
+                                       type: .application,
+                                       platform: .iOS,
+                                       sources: [.init(path: "generated.swift", optional: true)]
+                    )]
+                try spec.validate()
+            }
         }
     }
 }