diff --git a/share/trick/makefiles/Makefile.common b/share/trick/makefiles/Makefile.common
index bd22ec6c..d8dd88e5 100644
--- a/share/trick/makefiles/Makefile.common
+++ b/share/trick/makefiles/Makefile.common
@@ -50,6 +50,7 @@ ifndef TRICK_LD
     export TRICK_LD := $(LD)
 endif
 
+# setting makefile variable to shell environment variable (?)
 export TRICK_CFLAGS := $(TRICK_CFLAGS)
 export TRICK_CXXFLAGS := $(TRICK_CXXFLAGS)
 export TRICK_LDFLAGS := $(TRICK_LDFLAGS)
@@ -67,6 +68,7 @@ export TRICK_HOST_CPU := $(shell TRICK_FORCE_32BIT=$(TRICK_FORCE_32BIT) $(TRICK_
 export TRICK_EXEC_LINK_LIBS := ${PTHREAD_LIBS} $(PYTHON_LIB) $(UDUNITS_LDFLAGS) $(PLATFORM_LIBS) -lm -ldl
 export TRICK_LIBS := ${RPATH} -L${TRICK_LIB_DIR} -ltrick -ltrick_pyip -ltrick_comm -ltrick_math -ltrick_units -ltrick_mm
 export TRICK_SYSTEM_LDFLAGS := $(TRICK_SYSTEM_LDFLAGS)
+export TRICK_SYSTEM_ICG_EXCLUDE := $(TRICK_SYSTEM_ICG_EXCLUDE)
 export TRICK_SWIG_FLAGS := $(TRICK_SWIG_FLAGS)
 export TRICK_SWIG_CFLAGS := $(TRICK_SWIG_CFLAGS)
 export TRICK_CONVERT_SWIG_FLAGS := $(TRICK_CONVERT_SWIG_FLAGS)
diff --git a/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp b/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp
index b017e109..56cc3e9a 100644
--- a/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp
+++ b/trick_source/codegen/Interface_Code_Gen/HeaderSearchDirs.cpp
@@ -206,6 +206,7 @@ void HeaderSearchDirs::addSearchDirs ( std::vector<std::string> & include_dirs,
     AddCompilerBuiltInSearchDirs() ;
     ApplyHeaderSearchOptions() ;
     AddDirsAndFiles("TRICK_ICG_EXCLUDE", icg_exclude_dirs) ;
+    AddDirsAndFiles("TRICK_SYSTEM_ICG_EXCLUDE", icg_exclude_dirs) ;
     AddDirsAndFiles("TRICK_EXCLUDE", exclude_dirs) ;
     AddDirsAndFiles("TRICK_EXT_LIB_DIRS", ext_lib_dirs) ;
     AddDirsAndFiles("TRICK_ICG_NOCOMMENT", icg_nocomment_dirs) ;