diff --git a/Changes b/Changes
index c5547e5ef..ee05fe068 100644
--- a/Changes
+++ b/Changes
@@ -12,6 +12,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  Fix not in array context on non-power-of-two slices, msg2946. [Yu Sheng Lin]
 
+****  Fix system compile flags injection. [Gianfranco Costamagna]
+
 
 * Verilator 4.016 2016-06-16
 
diff --git a/configure.ac b/configure.ac
index 33b2f0638..6fa0f9841 100644
--- a/configure.ac
+++ b/configure.ac
@@ -91,10 +91,10 @@ AC_SUBST(CFG_WITH_PREC11)
 AC_MSG_RESULT($CFG_WITH_PREC11)
 
 # Compiler flags
-CFLAGS=-I${includedir}
-CPPFLAGS=-I${includedir}
-CXXFLAGS=-I${includedir}
-LDFLAGS=-L${libdir}
+CFLAGS+=" -I${includedir}"
+CPPFLAGS+=" -I${includedir}"
+CXXFLAGS+=" -I${includedir}"
+LDFLAGS+=" -L${libdir}"
 
 # Checks for programs.
 AC_PROG_CC
diff --git a/docs/CONTRIBUTORS b/docs/CONTRIBUTORS
index 3cd7de0aa..832b61548 100644
--- a/docs/CONTRIBUTORS
+++ b/docs/CONTRIBUTORS
@@ -4,8 +4,9 @@ under the Developer Certificate of Origin
 
 Please see the Verilator manual for additional contributors.
 
-Jeremy Bennett
 Alex Chadwick
+Gianfranco Costamagna
+Jeremy Bennett
 John Coiner
 Kanad Kanhere
 Richard Myers
diff --git a/src/Makefile_obj.in b/src/Makefile_obj.in
index 142f20a62..d7019eb86 100644
--- a/src/Makefile_obj.in
+++ b/src/Makefile_obj.in
@@ -60,6 +60,8 @@ pkgdatadir = @pkgdatadir@
 CFG_WITH_CCWARN = @CFG_WITH_CCWARN@
 CFG_WITH_DEFENV = @CFG_WITH_DEFENV@
 CPPFLAGS += @CPPFLAGS@
+CFLAGS += @CFLAGS@
+CXXFLAGS += @CXXFLAGS@
 LDFLAGS += @LDFLAGS@
 EXEEXT = @EXEEXT@
 CFG_CXXFLAGS_SRC = @CFG_CXXFLAGS_SRC@
@@ -135,7 +137,7 @@ VLCOVGEN = $(srcdir)/vlcovgen
 all: make_info $(TGT)
 
 make_info:
-	@echo "      Compile flags: " $(CXX) ${CPPFLAGS}
+	@echo "      Compile flags: " $(CXX) ${CFLAGS} ${CXXFLAGS} ${CPPFLAGS}
 
 clean mostlyclean distclean maintainer-clean::
 	-rm -f *.o *.d perlxsi.c *_gen_*
@@ -280,21 +282,21 @@ V3Number_test: V3Number_test.o
 	$(PERL) $(ASTGEN) -I$(srcdir) $*.cpp
 
 %.o:	%.cpp
-	$(OBJCACHE) ${CXX} ${CPPFLAGSWALL} -c $<
+	$(OBJCACHE) ${CXX} ${CXXFLAGS} ${CPPFLAGSWALL} -c $<
 %.o:	%.c
-	$(OBJCACHE) ${CC}  ${CPPFLAGSWALL} -c $<
+	$(OBJCACHE) ${CC}  ${CFLAGS} ${CPPFLAGSWALL} -c $<
 
 V3ParseLex.o:	V3ParseLex.cpp V3Lexer.yy.cpp V3ParseBison.c
-	$(OBJCACHE) ${CXX} ${CPPFLAGSPARSER} -c $<
+	$(OBJCACHE) ${CXX} ${CXXFLAGS} ${CPPFLAGSPARSER} -c $<
 
 V3ParseGrammar.o:	V3ParseGrammar.cpp V3ParseBison.c
-	$(OBJCACHE) ${CXX} ${CPPFLAGSPARSER} -c $<
+	$(OBJCACHE) ${CXX} ${CXXFLAGS} ${CPPFLAGSPARSER} -c $<
 
 V3ParseImp.o:	V3ParseImp.cpp V3ParseBison.c
-	$(OBJCACHE) ${CXX} ${CPPFLAGSPARSER} -c $<
+	$(OBJCACHE) ${CXX} ${CXXFLAGS} ${CPPFLAGSPARSER} -c $<
 
 V3PreProc.o:	V3PreProc.cpp V3PreLex.yy.cpp
-	$(OBJCACHE) ${CXX} ${CPPFLAGSPARSER} -c $<
+	$(OBJCACHE) ${CXX} ${CXXFLAGS} ${CPPFLAGSPARSER} -c $<
 
 #### Generated files