3 files changed, 14 insertions, 6 deletions
diff --git a/sources/shiboken6/generator/shiboken/cppgenerator.cpp b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
index 38e37c272..6b8d76bfc 100644
--- a/sources/shiboken6/generator/shiboken/cppgenerator.cpp
+++ b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
@@ -504,11 +504,10 @@ void CppGenerator::generateIncludes(TextStream &s, const GeneratorContext &class
     s << licenseComment() << '\n';
 
     const bool normalClass = !classContext.forSmartPointer();
-    if (normalClass && !avoidProtectedHack() && !metaClass->isNamespace()
-        && !metaClass->hasPrivateDestructor()) {
-        s << "//workaround to access protected functions\n";
-        s << "#define protected public\n\n";
-    }
+    // Normally only required for classes for which we want to generate protected API,
+    // but it needs to be generated into all files to ensure ODR for Unity builds.
+    if (!avoidProtectedHack())
+        s << HeaderGenerator::protectedHackDefine;
 
     QByteArrayList cppIncludes{"typeinfo", "iterator", // for containers
                                "cctype", "cstring"};
diff --git a/sources/shiboken6/generator/shiboken/headergenerator.cpp b/sources/shiboken6/generator/shiboken/headergenerator.cpp
index c7039d2b1..4d02bda3d 100644
--- a/sources/shiboken6/generator/shiboken/headergenerator.cpp
+++ b/sources/shiboken6/generator/shiboken/headergenerator.cpp
@@ -63,6 +63,13 @@ static bool alwaysGenerateDestructorDeclaration()
     return  clang::compiler() == Compiler::Msvc;
 }
 
+const char *HeaderGenerator::protectedHackDefine = R"(// Workaround to access protected functions
+#ifndef protected
+#  define protected public
+#endif
+
+)";
+
 QString HeaderGenerator::fileNameForContext(const GeneratorContext &context) const
 {
     return headerFileNameForContext(context);
@@ -99,7 +106,7 @@ void HeaderGenerator::generateClass(TextStream &s, const GeneratorContext &class
     s << "#define SBK_" << outerHeaderGuard << "_H\n\n";
 
     if (!avoidProtectedHack())
-        s << "#define protected public\n\n";
+        s << protectedHackDefine;
 
     //Includes
     s << metaClass->typeEntry()->include() << '\n';
diff --git a/sources/shiboken6/generator/shiboken/headergenerator.h b/sources/shiboken6/generator/shiboken/headergenerator.h
index 9fb0c3d95..6ebcc04ec 100644
--- a/sources/shiboken6/generator/shiboken/headergenerator.h
+++ b/sources/shiboken6/generator/shiboken/headergenerator.h
@@ -22,6 +22,8 @@ public:
 
     const char *name() const override { return "Header generator"; }
 
+    static const char *protectedHackDefine;
+
 protected:
     QString fileNameForContext(const GeneratorContext &context) const override;
     void generateClass(TextStream &s, const GeneratorContext &classContext) override;