diff --git a/winsup/cygserver/Makefile.am b/winsup/cygserver/Makefile.am
index d52f93ce0..ec7a62240 100644
--- a/winsup/cygserver/Makefile.am
+++ b/winsup/cygserver/Makefile.am
@@ -9,6 +9,7 @@
 include $(top_srcdir)/Makefile.am.common
 
 cygserver_flags=$(cxxflags_common) -Wimplicit-fallthrough=5 -Werror -DSYSCONFDIR="\"$(sysconfdir)\""
+AM_CXXFLAGS = $(CFLAGS)
 
 noinst_LIBRARIES = libcygserver.a
 sbin_PROGRAMS = cygserver
diff --git a/winsup/cygwin/Makefile.am b/winsup/cygwin/Makefile.am
index 63383a834..f39560863 100644
--- a/winsup/cygwin/Makefile.am
+++ b/winsup/cygwin/Makefile.am
@@ -531,6 +531,7 @@ endif
 
 override CFLAGS += $($(*F)_CFLAGS)
 override CXXFLAGS += $($(*F)_CFLAGS)
+AM_CXXFLAGS += $(CFLAGS)
 
 localtime_wrapper_CFLAGS=-I$(srcdir)/tzcode -fwrapv
 
diff --git a/winsup/utils/Makefile.am b/winsup/utils/Makefile.am
index 135e6143c..e12dfdd00 100644
--- a/winsup/utils/Makefile.am
+++ b/winsup/utils/Makefile.am
@@ -11,6 +11,7 @@ include $(top_srcdir)/Makefile.am.common
 CFLAGS_COMMON=-Wimplicit-fallthrough=4 -Werror -D_WIN32_WINNT=0x0a00 -DNTDDI_VERSION=WDK_NTDDI_VERSION
 AM_CFLAGS=$(cflags_common) $(CFLAGS_COMMON)
 AM_CXXFLAGS=$(cxxflags_common) $(CFLAGS_COMMON)
+AM_CXXFLAGS += $(CFLAGS)
 
 # Note that we call ps cygps here, so as not to collide with the
 # autogenerated texinfo rule with the name 'ps'...