diff --git a/sim/ChangeLog b/sim/ChangeLog
index a26cae9d2d8..16bca69cacc 100644
--- a/sim/ChangeLog
+++ b/sim/ChangeLog
@@ -1,3 +1,8 @@
+2021-05-04  Tom Tromey  <tromey@adacore.com>
+
+	* Makefile.in: Rebuild.
+	* Makefile.am (AM_CPPFLAGS): New variable.
+
 2021-05-04  Mike Frysinger  <vapier@gentoo.org>
 
 	* m4/sim_ac_toolchain.m4 (SIM_AC_TOOLCHAIN): Define AR_FOR_BUILD and
diff --git a/sim/Makefile.am b/sim/Makefile.am
index a68a964d87a..6696adc304a 100644
--- a/sim/Makefile.am
+++ b/sim/Makefile.am
@@ -35,6 +35,8 @@ CLEANFILES =
 DISTCLEANFILES =
 MOSTLYCLEANFILES = core
 
+AM_CPPFLAGS = -I$(srcroot)/include
+
 COMPILE_FOR_BUILD = $(CC_FOR_BUILD) $(AM_CPPFLAGS) $(CFLAGS_FOR_BUILD)
 LINK_FOR_BUILD = $(CC_FOR_BUILD) $(CFLAGS_FOR_BUILD) $(LDFLAGS_FOR_BUILD) -o $@
 
diff --git a/sim/Makefile.in b/sim/Makefile.in
index 890adab5072..5c997b0c118 100644
--- a/sim/Makefile.in
+++ b/sim/Makefile.in
@@ -682,6 +682,7 @@ CLEANFILES = testsuite/common/bits-gen testsuite/common/bits32m0.c \
 DISTCLEANFILES = 
 MOSTLYCLEANFILES = core $(am__append_3) site-srcdir.exp testrun.log \
 	testrun.sum
+AM_CPPFLAGS = -I$(srcroot)/include
 COMPILE_FOR_BUILD = $(CC_FOR_BUILD) $(AM_CPPFLAGS) $(CFLAGS_FOR_BUILD)
 LINK_FOR_BUILD = $(CC_FOR_BUILD) $(CFLAGS_FOR_BUILD) $(LDFLAGS_FOR_BUILD) -o $@
 @SIM_ENABLE_IGEN_TRUE@igen_libigen_a_SOURCES = \