diff --git a/Makefile.in b/Makefile.in
index a8a1ae68fa..9b51ae252c 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -47,7 +47,7 @@ PWD?=$(shell pwd)
 DESTDIR=
 bindir=$(prefix)/bin
 libdir=$(prefix)/lib
-incdir=$(prefix)/include
+incdir=$(prefix)/include/ghdl
 MKDIR=mkdir
 LN=ln -s
 CP=cp
@@ -433,7 +433,7 @@ libghdl.a: lib/$(libghdl_name)
 	ar rc $@ b~libghdl.o $(LIBGHDL_GRT_OBJS) `sed -e /^-/d < libghdl.bind`
 	grep adalib libghdl.bind | sed -e 's/^-L//' -e 's@adalib/@adalib/libgnat.a@' > libghdl.link
 
-$(srcdir)/src/synth/ghdlsynth_gates.h: $(srcdir)/src/synth/netlists.ads $(srcdir)/src/synth/netlists-gates.ads
+$(srcdir)/src/synth/include/synth_gates.h: $(srcdir)/src/synth/netlists.ads $(srcdir)/src/synth/netlists-gates.ads
 	echo "/* DO NOT MODIFY" > $@
 	echo "   This file is automatically generated by Makefile.  */" >> $@
 	echo "enum Module_Id {" >> $@
@@ -448,9 +448,9 @@ all.libghdl.true: lib/$(libghdl_name) libghdl.a
 all.libghdl.false:
 all.libghdl: all.libghdl.$(enable_libghdl)
 
-install.libghdl.include: install.dirs $(srcdir)/src/synth/ghdlsynth_gates.h
-	$(INSTALL_DATA) -p $(srcdir)/src/synth/ghdlsynth.h $(DESTDIR)$(incdir)/
-	$(INSTALL_DATA) -p $(srcdir)/src/synth/ghdlsynth_gates.h $(DESTDIR)$(incdir)/
+install.libghdl.include: install.dirs $(srcdir)/src/synth/include/synth_gates.h
+	$(INSTALL_DATA) -p $(srcdir)/src/synth/include/synth.h $(DESTDIR)$(incdir)
+	$(INSTALL_DATA) -p $(srcdir)/src/synth/include/synth_gates.h $(DESTDIR)$(incdir)
 
 install.libghdl.lib:
 	$(INSTALL_PROGRAM) -p lib/$(libghdl_name) $(DESTDIR)$(libdir)/
diff --git a/src/ghdldrv/ghdlvpi.adb b/src/ghdldrv/ghdlvpi.adb
index 35194f3bde..d2b2656cdc 100644
--- a/src/ghdldrv/ghdlvpi.adb
+++ b/src/ghdldrv/ghdlvpi.adb
@@ -37,7 +37,7 @@ package body Ghdlvpi is
       --  Compute install path
       Ghdllocal.Set_Exec_Prefix_From_Program_Name;
 
-      return Ghdllocal.Exec_Prefix.all & Directory_Separator & "include";
+      return Ghdllocal.Exec_Prefix.all & Directory_Separator & "include/ghdl";
    end Get_Vpi_Include_Dir;
 
    --  Return the lib directory.
diff --git a/src/synth/ghdlsynth.h b/src/synth/include/synth.h
similarity index 99%
rename from src/synth/ghdlsynth.h
rename to src/synth/include/synth.h
index b8387bf5a2..c89eab7fc3 100644
--- a/src/synth/ghdlsynth.h
+++ b/src/synth/include/synth.h
@@ -95,7 +95,7 @@ namespace GhdlSynth {
   typedef unsigned int Param_Idx;
   struct Pval { unsigned int id; };
 
-#include "ghdlsynth_gates.h"
+#include "ghdl/synth_gates.h"
 
   struct Module { unsigned int id; };
   inline bool is_valid(Module m) { return m.id != 0; }
diff --git a/src/synth/ghdlsynth_gates.h b/src/synth/include/synth_gates.h
similarity index 100%
rename from src/synth/ghdlsynth_gates.h
rename to src/synth/include/synth_gates.h
diff --git a/testsuite/gna/issue1226/vpi_plugin.c b/testsuite/gna/issue1226/vpi_plugin.c
index acdb79804a..b2c6c8dbe7 100644
--- a/testsuite/gna/issue1226/vpi_plugin.c
+++ b/testsuite/gna/issue1226/vpi_plugin.c
@@ -1,6 +1,6 @@
-#include<vpi_user.h>
-#include<inttypes.h>
-#include<stdio.h>
+#include <vpi_user.h>
+#include <inttypes.h>
+#include <stdio.h>
 
 //#define STOP_ITERATION 1000000000 // Initial value
 #define STOP_ITERATION 10000
diff --git a/testsuite/gna/issue1233/vpi_plugin.c b/testsuite/gna/issue1233/vpi_plugin.c
index dbfd0bf20a..9a9bd60df7 100644
--- a/testsuite/gna/issue1233/vpi_plugin.c
+++ b/testsuite/gna/issue1233/vpi_plugin.c
@@ -1,6 +1,6 @@
-#include<vpi_user.h>
-#include<inttypes.h>
-#include<stdio.h>
+#include <vpi_user.h>
+#include <inttypes.h>
+#include <stdio.h>
 
 //#define STOP_ITERATION 1000000000
 #define STOP_ITERATION 10000
diff --git a/testsuite/gna/issue1256/vpi_plugin.c b/testsuite/gna/issue1256/vpi_plugin.c
index 6d365cc82f..6771bc7d62 100644
--- a/testsuite/gna/issue1256/vpi_plugin.c
+++ b/testsuite/gna/issue1256/vpi_plugin.c
@@ -1,6 +1,6 @@
-#include<vpi_user.h>
-#include<inttypes.h>
-#include<stdio.h>
+#include <vpi_user.h>
+#include <inttypes.h>
+#include <stdio.h>
 
 #define STOP_ITERATION 5