diff --git a/reactos/tools/rbuild/backend/mingw/mingw.cpp b/reactos/tools/rbuild/backend/mingw/mingw.cpp
index 7afd7f047a3..46c2ea402e4 100644
--- a/reactos/tools/rbuild/backend/mingw/mingw.cpp
+++ b/reactos/tools/rbuild/backend/mingw/mingw.cpp
@@ -372,35 +372,31 @@ MingwBackend::GenerateHeader () const
 		ProjectNode.GetProjectFilename ().c_str () );
 }
 
-string
-MingwBackend::GenerateIncludesAndDefines ( IfableData& data ) const
-{
-	set<string> used_defs;
-	string includeParameters = MingwModuleHandler::GenerateGccIncludeParametersFromVector ( data.includes );
-	string defineParameters = MingwModuleHandler::GenerateGccDefineParametersFromVector ( data.defines, used_defs );
-	return includeParameters + " " + defineParameters;
-}
-
 void
 MingwBackend::GenerateProjectCFlagsMacro ( const char* assignmentOperation,
-                                           IfableData& data ) const
+                                           const IfableData& data ) const
 {
-	fprintf (
-		fMakefile,
-		"PROJECT_CFLAGS %s",
-		assignmentOperation );
-	
-	fprintf ( fMakefile,
-	          " %s",
-	          GenerateIncludesAndDefines ( data ).c_str() );
+	set<string> used_defs;
 
-	fprintf ( fMakefile, "\n" );
+	if ( data.includes.size () > 0 )
+		fprintf (
+			fMakefile,
+			"PROJECT_CFLAGS %s %s\n",
+			assignmentOperation,
+			MingwModuleHandler::GenerateGccIncludeParametersFromVector ( data.includes ).c_str ());
+
+	if ( data.defines.size () > 0 )
+		fprintf (
+			fMakefile,
+			"PROJECT_CDEFINES %s %s\n",
+			assignmentOperation,
+			MingwModuleHandler::GenerateGccDefineParametersFromVector ( data.defines, used_defs ).c_str ());
 }
 
 void
 MingwBackend::GenerateGlobalCFlagsAndProperties (
 	const char* assignmentOperation,
-	IfableData& data ) const
+	const IfableData& data ) const
 {
 	size_t i;
 
@@ -420,7 +416,7 @@ MingwBackend::GenerateGlobalCFlagsAndProperties (
 
 	for ( i = 0; i < data.ifs.size(); i++ )
 	{
-		If& rIf = *data.ifs[i];
+		const If& rIf = *data.ifs[i];
 		if ( rIf.data.defines.size()
 			|| rIf.data.includes.size()
 			|| rIf.data.ifs.size() )
@@ -523,8 +519,8 @@ MingwBackend::GenerateGlobalVariables () const
 	GenerateGlobalCFlagsAndProperties ( "=", ProjectNode.non_if_data );
 	GenerateProjectGccOptions ( "=", ProjectNode.non_if_data );
 
-	fprintf ( fMakefile, "PROJECT_RCFLAGS := $(PROJECT_CFLAGS)\n" );
-	fprintf ( fMakefile, "PROJECT_WIDLFLAGS := $(PROJECT_CFLAGS)\n" );
+	fprintf ( fMakefile, "PROJECT_RCFLAGS := $(PROJECT_CFLAGS) $(PROJECT_CDEFINES)\n" );
+	fprintf ( fMakefile, "PROJECT_WIDLFLAGS := $(PROJECT_CFLAGS) $(PROJECT_CDEFINES)\n" );
 	fprintf ( fMakefile, "PROJECT_LFLAGS := %s\n",
 	          GenerateProjectLFLAGS ().c_str () );
 	fprintf ( fMakefile, "PROJECT_CFLAGS += -Wall\n" );
diff --git a/reactos/tools/rbuild/backend/mingw/mingw.h b/reactos/tools/rbuild/backend/mingw/mingw.h
index 65e61e86c03..9b08eed9ceb 100644
--- a/reactos/tools/rbuild/backend/mingw/mingw.h
+++ b/reactos/tools/rbuild/backend/mingw/mingw.h
@@ -62,11 +62,10 @@ private:
 	void CreateMakefile ();
 	void CloseMakefile () const;
 	void GenerateHeader () const;
-	std::string GenerateIncludesAndDefines ( IfableData& data ) const;
 	void GenerateProjectCFlagsMacro ( const char* assignmentOperation,
-	                                  IfableData& data ) const;
+	                                  const IfableData& data ) const;
 	void GenerateGlobalCFlagsAndProperties ( const char* op,
-	                                         IfableData& data ) const;
+	                                         const IfableData& data ) const;
 	void GenerateProjectGccOptionsMacro ( const char* assignmentOperation,
 	                                      IfableData& data ) const;
 	void GenerateProjectGccOptions ( const char* assignmentOperation,
diff --git a/reactos/tools/rbuild/backend/mingw/modulehandler.cpp b/reactos/tools/rbuild/backend/mingw/modulehandler.cpp
index 677ef6e9b14..938e0324ada 100644
--- a/reactos/tools/rbuild/backend/mingw/modulehandler.cpp
+++ b/reactos/tools/rbuild/backend/mingw/modulehandler.cpp
@@ -629,7 +629,7 @@ MingwModuleHandler::GetObjectFilenames ()
 /* static */ string
 MingwModuleHandler::GenerateGccDefineParametersFromVector (
 	const vector<Define*>& defines,
-        set<string>& used_defs)
+	set<string>& used_defs)
 {
 	string parameters;
 
@@ -640,8 +640,8 @@ MingwModuleHandler::GenerateGccDefineParametersFromVector (
 			continue;
 		if (parameters.length () > 0)
 			parameters += " ";
-                if (define.name.find('(') != string::npos)
-                        parameters += "$(QT)";
+		if (define.name.find('(') != string::npos)
+			parameters += "$(QT)";
 		parameters += "-D";
 		parameters += define.name;
 		if (define.value.length () > 0)
@@ -649,8 +649,8 @@ MingwModuleHandler::GenerateGccDefineParametersFromVector (
 			parameters += "=";
 			parameters += define.value;
 		}
-                if (define.name.find('(') != string::npos)
-                        parameters += "$(QT)";
+		if (define.name.find('(') != string::npos)
+			parameters += "$(QT)";
 		used_defs.insert(used_defs.begin(),define.name);
 	}
 	return parameters;
@@ -659,7 +659,7 @@ MingwModuleHandler::GenerateGccDefineParametersFromVector (
 string
 MingwModuleHandler::GenerateGccDefineParameters () const
 {
-        set<string> used_defs;
+	set<string> used_defs;
 	string parameters = GenerateGccDefineParametersFromVector ( module.project.non_if_data.defines, used_defs );
 	string s = GenerateGccDefineParametersFromVector ( module.non_if_data.defines, used_defs );
 	if ( s.length () > 0 )
@@ -765,7 +765,8 @@ void
 MingwModuleHandler::GenerateMacro (
 	const char* assignmentOperation,
 	const string& macro,
-	const IfableData& data )
+	const IfableData& data,
+	set<string> *used_defs )
 {
 	size_t i;
 	bool generateAssignment;
@@ -806,7 +807,14 @@ MingwModuleHandler::GenerateMacro (
 	}
 	for ( i = 0; i < data.defines.size(); i++ )
 	{
-		Define& d = *data.defines[i];
+		const Define& d = *data.defines[i];
+		if (used_defs && used_defs->find(d.name) != used_defs->end())
+		{
+			if ( backend->configuration.Verbose )
+				printf("%s define overridden in '%s' module\n",
+					d.name.c_str (), module.name.c_str () );
+			continue;
+		}
 		fprintf (
 			fMakefile,
 			" -D%s",
@@ -816,6 +824,8 @@ MingwModuleHandler::GenerateMacro (
 				fMakefile,
 				"=%s",
 				d.value.c_str() );
+		if (used_defs)
+			used_defs->insert(used_defs->begin(), d.name);
 	}
 	if ( generateAssignment )
 	{
@@ -827,16 +837,19 @@ void
 MingwModuleHandler::GenerateMacros (
 	const char* assignmentOperation,
 	const IfableData& data,
-	const vector<LinkerFlag*>* linkerFlags )
+	const vector<LinkerFlag*>* linkerFlags,
+	set<string>& used_defs )
 {
 	size_t i;
 
 	GenerateMacro ( assignmentOperation,
 	                cflagsMacro,
-	                data );
+	                data,
+	                &used_defs );
 	GenerateMacro ( assignmentOperation,
 	                windresflagsMacro,
-	                data );
+	                data,
+	                NULL );
 
 	if ( linkerFlags != NULL )
 	{
@@ -886,7 +899,8 @@ MingwModuleHandler::GenerateMacros (
 			GenerateMacros (
 				"+=",
 				rIf.data,
-				NULL );
+				NULL,
+				used_defs );
 			fprintf (
 				fMakefile,
 				"endif\n\n" );
@@ -2020,6 +2034,8 @@ MingwModuleHandler::GetRpcHeaderDependencies (
 void
 MingwModuleHandler::GenerateOtherMacros ()
 {
+	set<string> used_defs;
+
 	cflagsMacro = ssprintf ("%s_CFLAGS", module.name.c_str ());
 	nasmflagsMacro = ssprintf ("%s_NASMFLAGS", module.name.c_str ());
 	windresflagsMacro = ssprintf ("%s_RCFLAGS", module.name.c_str ());
@@ -2031,7 +2047,14 @@ MingwModuleHandler::GenerateOtherMacros ()
 	GenerateMacros (
 		"=",
 		module.non_if_data,
-		&module.linkerFlags );
+		&module.linkerFlags,
+		used_defs );
+
+	GenerateMacros (
+		"+=",
+		module.project.non_if_data,
+		NULL,
+		used_defs );
 
 	vector<FileLocation> s;
 	if ( module.importLibrary )
diff --git a/reactos/tools/rbuild/backend/mingw/modulehandler.h b/reactos/tools/rbuild/backend/mingw/modulehandler.h
index d5a1d274f7c..96cb2ba49ca 100644
--- a/reactos/tools/rbuild/backend/mingw/modulehandler.h
+++ b/reactos/tools/rbuild/backend/mingw/modulehandler.h
@@ -136,10 +136,12 @@ private:
 	std::string GenerateLinkerParameters () const;
 	void GenerateMacro ( const char* assignmentOperation,
 	                     const std::string& macro,
-	                     const IfableData& data );
+	                     const IfableData& data,
+	                     std::set<std::string>* used_defs );
 	void GenerateMacros ( const char* op,
 	                      const IfableData& data,
-	                      const std::vector<LinkerFlag*>* linkerFlags );
+	                      const std::vector<LinkerFlag*>* linkerFlags,
+	                      std::set<std::string>& used_defs );
 	void GenerateSourceMacros ( const char* assignmentOperation,
 	                            const IfableData& data );
 	void GenerateObjectMacros ( const char* assignmentOperation,