diff --git a/Sources/MockingbirdCli/Interface/Generator+PruningPipeline.swift b/Sources/MockingbirdCli/Interface/Generator+PruningPipeline.swift
index bb788aea..4af54e49 100644
--- a/Sources/MockingbirdCli/Interface/Generator+PruningPipeline.swift
+++ b/Sources/MockingbirdCli/Interface/Generator+PruningPipeline.swift
@@ -82,7 +82,8 @@ extension Generator {
       self.findMockedTypesOperation = findMockedTypesOperation
     }
     
-    func cache(cliVersion: String,
+    func cache(projectHash: String,
+               cliVersion: String,
                configHash: String,
                sourceRoot: Path,
                cacheDirectory: Path,
@@ -95,6 +96,7 @@ extension Generator {
         target = try TestTarget(from: pipelineTarget,
                                 sourceRoot: sourceRoot,
                                 mockedTypeNames: mockedTypeNames,
+                                projectHash: projectHash,
                                 cliVersion: cliVersion,
                                 configHash: configHash,
                                 environment: environment)
@@ -106,6 +108,7 @@ extension Generator {
         target = try TestTarget(from: pipelineTarget,
                                 sourceRoot: sourceRoot,
                                 mockedTypeNames: mockedTypeNames,
+                                projectHash: projectHash,
                                 cliVersion: cliVersion,
                                 configHash: configHash,
                                 environment: environment)
@@ -119,6 +122,7 @@ extension Generator {
   }
   
   func findCachedTestTarget(for targetName: String,
+                            projectHash: String,
                             cliVersion: String,
                             configHash: String,
                             cacheDirectory: Path,
@@ -140,6 +144,11 @@ extension Generator {
       return nil
     }
     
+    guard target.projectHash == projectHash else {
+      log("Invalidated cached test target metadata for \(targetName.singleQuoted) because the project hash changed from \(target.projectHash.singleQuoted) to \(projectHash.singleQuoted)")
+      return nil
+    }
+    
     guard cliVersion == target.cliVersion else {
       log("Invalidated cached test target metadata for \(target.name.singleQuoted) because the CLI version changed from \(target.cliVersion.singleQuoted) to \(cliVersion.singleQuoted)")
       return nil
diff --git a/Sources/MockingbirdCli/Interface/Generator.swift b/Sources/MockingbirdCli/Interface/Generator.swift
index 1e38c717..c41b7e47 100644
--- a/Sources/MockingbirdCli/Interface/Generator.swift
+++ b/Sources/MockingbirdCli/Interface/Generator.swift
@@ -107,7 +107,9 @@ class Generator {
   func getCachedTestTarget(targetName: String) -> TargetType? {
     guard !config.disableThunkStubs,
       let cacheDirectory = testTargetCacheDirectory,
+      let projectHash = getProjectHash(config.projectPath),
       let cachedTarget = findCachedTestTarget(for: targetName,
+                                              projectHash: projectHash,
                                               cliVersion: cliVersion,
                                               configHash: configHash,
                                               cacheDirectory: cacheDirectory,
@@ -194,25 +196,26 @@ class Generator {
   }
   
   func cachePipelines(sourcePipelines: [Pipeline], pruningPipeline: PruningPipeline?) throws {
+    guard let projectHash = getProjectHash(config.projectPath) else { return }
+    
     // Cache source targets for generation.
-    if let projectHash = getProjectHash(config.projectPath) {
-      try sourceTargetCacheDirectory.mkpath()
-      try sourcePipelines.forEach({
-        try $0.cache(projectHash: projectHash,
-                     cliVersion: cliVersion,
-                     configHash: configHash,
-                     sourceRoot: config.sourceRoot,
-                     cacheDirectory: sourceTargetCacheDirectory,
-                     environment: getBuildEnvironment)
-      })
-    }
+    try sourceTargetCacheDirectory.mkpath()
+    try sourcePipelines.forEach({
+      try $0.cache(projectHash: projectHash,
+                   cliVersion: cliVersion,
+                   configHash: configHash,
+                   sourceRoot: config.sourceRoot,
+                   cacheDirectory: sourceTargetCacheDirectory,
+                   environment: getBuildEnvironment)
+    })
     
     // Cache test target for thunk pruning.
     if !config.disableThunkStubs {
       if let testTargetCacheDirectory = testTargetCacheDirectory,
         let environmentSourceRoot = config.environmentSourceRoot {
         try testTargetCacheDirectory.mkpath()
-        try pruningPipeline?.cache(cliVersion: cliVersion,
+        try pruningPipeline?.cache(projectHash: projectHash,
+                                   cliVersion: cliVersion,
                                    configHash: configHash,
                                    sourceRoot: environmentSourceRoot,
                                    cacheDirectory: testTargetCacheDirectory,
diff --git a/Sources/MockingbirdGenerator/Parser/Project/TestTarget.swift b/Sources/MockingbirdGenerator/Parser/Project/TestTarget.swift
index 9439750b..4e12398f 100644
--- a/Sources/MockingbirdGenerator/Parser/Project/TestTarget.swift
+++ b/Sources/MockingbirdGenerator/Parser/Project/TestTarget.swift
@@ -10,11 +10,13 @@ import PathKit
 
 public class TestTarget: CodableTarget {
   public let mockedTypeNames: [Path: Set<String>]
+  public let projectHash: String
   public let cliVersion: String
   public let configHash: String
   
   enum CodingKeys: String, CodingKey {
     case mockedTypeNames
+    case projectHash
     case cliVersion
     case configHash
   }
@@ -22,10 +24,12 @@ public class TestTarget: CodableTarget {
   public init<T: Target>(from target: T,
                          sourceRoot: Path,
                          mockedTypeNames: [Path: Set<String>],
+                         projectHash: String,
                          cliVersion: String,
                          configHash: String,
                          environment: () -> [String: Any]) throws {
     self.mockedTypeNames = mockedTypeNames
+    self.projectHash = projectHash
     self.cliVersion = cliVersion
     self.configHash = configHash
     
@@ -41,6 +45,7 @@ public class TestTarget: CodableTarget {
     let container = try decoder.container(keyedBy: CodingKeys.self)
     
     self.mockedTypeNames = try container.decode([Path: Set<String>].self, forKey: .mockedTypeNames)
+    self.projectHash = try container.decode(String.self, forKey: .projectHash)
     self.cliVersion = try container.decode(String.self, forKey: .cliVersion)
     self.configHash = try container.decode(String.self, forKey: .configHash)
     
@@ -51,6 +56,7 @@ public class TestTarget: CodableTarget {
     var container = encoder.container(keyedBy: CodingKeys.self)
     
     try container.encode(mockedTypeNames, forKey: .mockedTypeNames)
+    try container.encode(projectHash, forKey: .projectHash)
     try container.encode(cliVersion, forKey: .cliVersion)
     try container.encode(configHash, forKey: .configHash)