diff --git a/Source/cmExportFileGenerator.h b/Source/cmExportFileGenerator.h
index 5234597a3..d106ab747 100644
--- a/Source/cmExportFileGenerator.h
+++ b/Source/cmExportFileGenerator.h
@@ -78,27 +78,28 @@ protected:
                             std::vector<std::string>& missingTargets);
 
   // Methods to implement export file code generation.
-  void GeneratePolicyHeaderCode(std::ostream& os);
-  void GeneratePolicyFooterCode(std::ostream& os);
-  void GenerateImportHeaderCode(std::ostream& os,
-                                const std::string& config = "");
-  void GenerateImportFooterCode(std::ostream& os);
+  virtual void GeneratePolicyHeaderCode(std::ostream& os);
+  virtual void GeneratePolicyFooterCode(std::ostream& os);
+  virtual void GenerateImportHeaderCode(std::ostream& os,
+                                        const std::string& config = "");
+  virtual void GenerateImportFooterCode(std::ostream& os);
   void GenerateImportVersionCode(std::ostream& os);
-  void GenerateImportTargetCode(std::ostream& os,
-                                cmGeneratorTarget const* target);
-  void GenerateImportPropertyCode(std::ostream& os, const std::string& config,
-                                  cmGeneratorTarget const* target,
-                                  ImportPropertyMap const& properties);
-  void GenerateImportedFileChecksCode(
+  virtual void GenerateImportTargetCode(std::ostream& os,
+                                        cmGeneratorTarget const* target);
+  virtual void GenerateImportPropertyCode(std::ostream& os,
+                                          const std::string& config,
+                                          cmGeneratorTarget const* target,
+                                          ImportPropertyMap const& properties);
+  virtual void GenerateImportedFileChecksCode(
     std::ostream& os, cmGeneratorTarget* target,
     ImportPropertyMap const& properties,
     const std::set<std::string>& importedLocations);
-  void GenerateImportedFileCheckLoop(std::ostream& os);
-  void GenerateMissingTargetsCheckCode(
+  virtual void GenerateImportedFileCheckLoop(std::ostream& os);
+  virtual void GenerateMissingTargetsCheckCode(
     std::ostream& os, const std::vector<std::string>& missingTargets);
 
-  void GenerateExpectedTargetsCode(std::ostream& os,
-                                   const std::string& expectedTargets);
+  virtual void GenerateExpectedTargetsCode(std::ostream& os,
+                                           const std::string& expectedTargets);
 
   // Collect properties with detailed information about targets beyond
   // their location on disk.
@@ -142,9 +143,9 @@ protected:
                                  ImportPropertyMap& properties);
   void PopulateCompatibleInterfaceProperties(cmGeneratorTarget* target,
                                              ImportPropertyMap& properties);
-  void GenerateInterfaceProperties(cmGeneratorTarget const* target,
-                                   std::ostream& os,
-                                   const ImportPropertyMap& properties);
+  virtual void GenerateInterfaceProperties(
+    cmGeneratorTarget const* target, std::ostream& os,
+    const ImportPropertyMap& properties);
   void PopulateIncludeDirectoriesInterface(
     cmTargetExport* target,
     cmGeneratorExpression::PreprocessContext preprocessRule,
@@ -171,8 +172,8 @@ protected:
     std::vector<std::string>& missingTargets,
     FreeTargetsReplace replace = NoReplaceFreeTargets);
 
-  void GenerateRequiredCMakeVersion(std::ostream& os,
-                                    const char* versionString);
+  virtual void GenerateRequiredCMakeVersion(std::ostream& os,
+                                            const char* versionString);
 
   // The namespace in which the exports are placed in the generated file.
   std::string Namespace;
diff --git a/Source/cmExportInstallFileGenerator.h b/Source/cmExportInstallFileGenerator.h
index fe34efde3..63f2d4039 100644
--- a/Source/cmExportInstallFileGenerator.h
+++ b/Source/cmExportInstallFileGenerator.h
@@ -81,16 +81,16 @@ protected:
                                           const std::string& name);
 
   /** Generate the relative import prefix.  */
-  void GenerateImportPrefix(std::ostream&);
+  virtual void GenerateImportPrefix(std::ostream&);
 
   /** Generate the relative import prefix.  */
-  void LoadConfigFiles(std::ostream&);
+  virtual void LoadConfigFiles(std::ostream&);
 
-  void CleanupTemporaryVariables(std::ostream&);
+  virtual void CleanupTemporaryVariables(std::ostream&);
 
   /** Generate a per-configuration file for the targets.  */
-  bool GenerateImportFileConfig(const std::string& config,
-                                std::vector<std::string>& missingTargets);
+  virtual bool GenerateImportFileConfig(
+    const std::string& config, std::vector<std::string>& missingTargets);
 
   /** Fill in properties indicating installed file locations.  */
   void SetImportLocationProperty(const std::string& config,