diff --git a/libphobos/Makefile.am b/libphobos/Makefile.am
index 84d80016025..874b3a25d02 100644
--- a/libphobos/Makefile.am
+++ b/libphobos/Makefile.am
@@ -33,14 +33,14 @@ AM_MAKEFLAGS = \
 	"AR_FLAGS=$(AR_FLAGS)" \
 	"CC_FOR_BUILD=$(CC_FOR_BUILD)" \
 	"CC_FOR_TARGET=$(CC_FOR_TARGET)" \
-	"CCASFLAGS=$(CCASFLAGS) $(CET_FLAGS)" \
-	"CFLAGS=$(CFLAGS) $(CET_FLAGS)" \
-	"CXXFLAGS=$(CXXFLAGS) $(CET_FLAGS)" \
+	"CCASFLAGS=$(CCASFLAGS)" \
+	"CFLAGS=$(CFLAGS)" \
+	"CXXFLAGS=$(CXXFLAGS)" \
 	"CFLAGS_FOR_BUILD=$(CFLAGS_FOR_BUILD)" \
-	"CFLAGS_FOR_TARGET=$(CFLAGS_FOR_TARGET) $(CET_FLAGS)" \
+	"CFLAGS_FOR_TARGET=$(CFLAGS_FOR_TARGET)" \
 	"GDC_FOR_TARGET=$(GDC_FOR_TARGET)" \
 	"GDC=$(GDC)" \
-	"GDCFLAGS=$(GDCFLAGS) $(CET_FLAGS)" \
+	"GDCFLAGS=$(GDCFLAGS)" \
 	"INSTALL=$(INSTALL)" \
 	"INSTALL_DATA=$(INSTALL_DATA)" \
 	"INSTALL_PROGRAM=$(INSTALL_PROGRAM)" \
diff --git a/libphobos/Makefile.in b/libphobos/Makefile.in
index f6cba17159f..f692b2f719e 100644
--- a/libphobos/Makefile.in
+++ b/libphobos/Makefile.in
@@ -207,6 +207,7 @@ CC = @CC@
 CCAS = @CCAS@
 CCASFLAGS = @CCASFLAGS@
 CC_FOR_BUILD = @CC_FOR_BUILD@
+CET_DFLAGS = @CET_DFLAGS@
 CET_FLAGS = @CET_FLAGS@
 CFLAGS = @CFLAGS@
 CFLAGS_FOR_BUILD = @CFLAGS_FOR_BUILD@
@@ -216,7 +217,6 @@ CPPFLAGS = @CPPFLAGS@
 CYGPATH_W = @CYGPATH_W@
 DCFG_ARM_EABI_UNWINDER = @DCFG_ARM_EABI_UNWINDER@
 DCFG_DLPI_TLS_MODID = @DCFG_DLPI_TLS_MODID@
-DCFG_ENABLE_CET = @DCFG_ENABLE_CET@
 DCFG_HAVE_64BIT_ATOMICS = @DCFG_HAVE_64BIT_ATOMICS@
 DCFG_HAVE_ATOMIC_BUILTINS = @DCFG_HAVE_ATOMIC_BUILTINS@
 DCFG_HAVE_LIBATOMIC = @DCFG_HAVE_LIBATOMIC@
@@ -355,14 +355,14 @@ AM_MAKEFLAGS = \
 	"AR_FLAGS=$(AR_FLAGS)" \
 	"CC_FOR_BUILD=$(CC_FOR_BUILD)" \
 	"CC_FOR_TARGET=$(CC_FOR_TARGET)" \
-	"CCASFLAGS=$(CCASFLAGS) $(CET_FLAGS)" \
-	"CFLAGS=$(CFLAGS) $(CET_FLAGS)" \
-	"CXXFLAGS=$(CXXFLAGS) $(CET_FLAGS)" \
+	"CCASFLAGS=$(CCASFLAGS)" \
+	"CFLAGS=$(CFLAGS)" \
+	"CXXFLAGS=$(CXXFLAGS)" \
 	"CFLAGS_FOR_BUILD=$(CFLAGS_FOR_BUILD)" \
-	"CFLAGS_FOR_TARGET=$(CFLAGS_FOR_TARGET) $(CET_FLAGS)" \
+	"CFLAGS_FOR_TARGET=$(CFLAGS_FOR_TARGET)" \
 	"GDC_FOR_TARGET=$(GDC_FOR_TARGET)" \
 	"GDC=$(GDC)" \
-	"GDCFLAGS=$(GDCFLAGS) $(CET_FLAGS)" \
+	"GDCFLAGS=$(GDCFLAGS)" \
 	"INSTALL=$(INSTALL)" \
 	"INSTALL_DATA=$(INSTALL_DATA)" \
 	"INSTALL_PROGRAM=$(INSTALL_PROGRAM)" \
diff --git a/libphobos/configure b/libphobos/configure
index 86a0aba6976..4c1116d6f80 100755
--- a/libphobos/configure
+++ b/libphobos/configure
@@ -722,7 +722,7 @@ LIBTOOL
 CFLAGS_FOR_BUILD
 CC_FOR_BUILD
 AR
-DCFG_ENABLE_CET
+CET_DFLAGS
 CET_FLAGS
 RANLIB
 MAINT
@@ -5651,12 +5651,11 @@ $as_echo "no" >&6; }
 fi
 
 
-if test x$enable_cet = xyes; then :
-  DCFG_ENABLE_CET=true
-else
-  DCFG_ENABLE_CET=false
-fi
+# To ensure that runtime code for CET is compiled in, add in D version flags.
+if test "$enable_cet" = yes; then
+  CET_DFLAGS="$CET_FLAGS -fversion=CET"
 
+fi
 
 # This should be inherited in the recursive make, but ensure it is defined.
 test "$AR" || AR=ar
@@ -11745,7 +11744,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11748 "configure"
+#line 11747 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11851,7 +11850,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11854 "configure"
+#line 11853 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
diff --git a/libphobos/configure.ac b/libphobos/configure.ac
index 97f96934aaf..bf21128bd50 100644
--- a/libphobos/configure.ac
+++ b/libphobos/configure.ac
@@ -68,9 +68,11 @@ AC_PROG_MAKE_SET
 # Add CET specific flags if CET is enabled
 GCC_CET_FLAGS(CET_FLAGS)
 AC_SUBST(CET_FLAGS)
-AS_IF([test x$enable_cet = xyes],
-  [DCFG_ENABLE_CET=true], [DCFG_ENABLE_CET=false])
-AC_SUBST(DCFG_ENABLE_CET)
+# To ensure that runtime code for CET is compiled in, add in D version flags.
+if test "$enable_cet" = yes; then
+  CET_DFLAGS="$CET_FLAGS -fversion=CET"
+  AC_SUBST(CET_DFLAGS)
+fi
 
 # This should be inherited in the recursive make, but ensure it is defined.
 test "$AR" || AR=ar
diff --git a/libphobos/libdruntime/Makefile.am b/libphobos/libdruntime/Makefile.am
index 1d340a0041c..4136642beeb 100644
--- a/libphobos/libdruntime/Makefile.am
+++ b/libphobos/libdruntime/Makefile.am
@@ -24,7 +24,11 @@ D_EXTRA_DFLAGS=-nostdinc -I $(srcdir) -I .
 # D flags for compilation
 AM_DFLAGS= \
 	$(phobos_compiler_pic_flag) \
-	$(WARN_DFLAGS) $(CHECKING_DFLAGS)
+	$(WARN_DFLAGS) $(CHECKING_DFLAGS) $(CET_DFLAGS)
+
+# Flags for other kinds of sources
+AM_CFLAGS=$(CET_FLAGS)
+AM_CCASFLAGS=$(CET_FLAGS)
 
 # Install all D and DI files
 ALL_DRUNTIME_INSTALL_DSOURCES = $(DRUNTIME_DSOURCES) \
diff --git a/libphobos/libdruntime/Makefile.in b/libphobos/libdruntime/Makefile.in
index 28b4333838f..d0bb3242c4f 100644
--- a/libphobos/libdruntime/Makefile.in
+++ b/libphobos/libdruntime/Makefile.in
@@ -567,6 +567,7 @@ CC = @CC@
 CCAS = @CCAS@
 CCASFLAGS = @CCASFLAGS@
 CC_FOR_BUILD = @CC_FOR_BUILD@
+CET_DFLAGS = @CET_DFLAGS@
 CET_FLAGS = @CET_FLAGS@
 CFLAGS = @CFLAGS@
 CFLAGS_FOR_BUILD = @CFLAGS_FOR_BUILD@
@@ -576,7 +577,6 @@ CPPFLAGS = @CPPFLAGS@
 CYGPATH_W = @CYGPATH_W@
 DCFG_ARM_EABI_UNWINDER = @DCFG_ARM_EABI_UNWINDER@
 DCFG_DLPI_TLS_MODID = @DCFG_DLPI_TLS_MODID@
-DCFG_ENABLE_CET = @DCFG_ENABLE_CET@
 DCFG_HAVE_64BIT_ATOMICS = @DCFG_HAVE_64BIT_ATOMICS@
 DCFG_HAVE_ATOMIC_BUILTINS = @DCFG_HAVE_ATOMIC_BUILTINS@
 DCFG_HAVE_LIBATOMIC = @DCFG_HAVE_LIBATOMIC@
@@ -719,9 +719,13 @@ D_EXTRA_DFLAGS = -nostdinc -I $(srcdir) -I .
 # D flags for compilation
 AM_DFLAGS = \
 	$(phobos_compiler_pic_flag) \
-	$(WARN_DFLAGS) $(CHECKING_DFLAGS)
+	$(WARN_DFLAGS) $(CHECKING_DFLAGS) $(CET_DFLAGS)
 
 
+# Flags for other kinds of sources
+AM_CFLAGS = $(CET_FLAGS)
+AM_CCASFLAGS = $(CET_FLAGS)
+
 # Install all D and DI files
 ALL_DRUNTIME_INSTALL_DSOURCES = $(DRUNTIME_DSOURCES) \
 	$(DRUNTIME_DSOURCES_BIONIC) $(DRUNTIME_DSOURCES_DARWIN) \
diff --git a/libphobos/libdruntime/core/thread.d b/libphobos/libdruntime/core/thread.d
index 8f4603d3d2f..eaf088d53c1 100644
--- a/libphobos/libdruntime/core/thread.d
+++ b/libphobos/libdruntime/core/thread.d
@@ -3586,45 +3586,44 @@ private
     }
     else version (X86)
     {
-        import gcc.config;
-
         version = AlignFiberStackTo16Byte;
 
-        static if (!GNU_Enable_CET)
+        version (CET)
+        {
+            // fiber_switchContext does not support shadow stack from
+            // Intel CET.  So use ucontext implementation.
+        }
+        else
         {
             version = AsmExternal;
 
             version (MinGW)
-            {
                 version = GNU_AsmX86_Windows;
-            }
             else version (Posix)
-            {
                 version = AsmX86_Posix;
-            }
         }
     }
     else version (X86_64)
     {
-        import gcc.config;
-
         version = AlignFiberStackTo16Byte;
 
-        static if (!GNU_Enable_CET)
+        version (CET)
         {
-            version (D_X32)
-            {
-                // let X32 be handled by ucontext swapcontext
-            }
-            else
-            {
-                version = AsmExternal;
+            // fiber_switchContext does not support shadow stack from
+            // Intel CET.  So use ucontext implementation.
+        }
+        else version (D_X32)
+        {
+            // let X32 be handled by ucontext swapcontext
+        }
+        else
+        {
+            version = AsmExternal;
 
-                version (MinGW)
-                    version = GNU_AsmX86_64_Windows;
-                else version (Posix)
-                    version = AsmX86_64_Posix;
-            }
+            version (MinGW)
+                version = GNU_AsmX86_64_Windows;
+            else version (Posix)
+                version = AsmX86_64_Posix;
         }
     }
     else version (PPC)
diff --git a/libphobos/libdruntime/gcc/config.d.in b/libphobos/libdruntime/gcc/config.d.in
index 9ac7d055271..6301aaff069 100644
--- a/libphobos/libdruntime/gcc/config.d.in
+++ b/libphobos/libdruntime/gcc/config.d.in
@@ -49,6 +49,3 @@ enum GNU_Have_LibAtomic = @DCFG_HAVE_LIBATOMIC@;
 
 // Do we have qsort_r function
 enum Have_Qsort_R = @DCFG_HAVE_QSORT_R@;
-
-// Whether libphobos been configured with --enable-cet.
-enum GNU_Enable_CET = @DCFG_ENABLE_CET@;
diff --git a/libphobos/src/Makefile.am b/libphobos/src/Makefile.am
index 9fb416ecc32..3769d8efafc 100644
--- a/libphobos/src/Makefile.am
+++ b/libphobos/src/Makefile.am
@@ -25,7 +25,10 @@ D_EXTRA_DFLAGS=-nostdinc -I $(srcdir) \
 # D flags for compilation
 AM_DFLAGS= \
 	$(phobos_compiler_pic_flag) \
-	$(WARN_DFLAGS) $(CHECKING_DFLAGS)
+	$(WARN_DFLAGS) $(CHECKING_DFLAGS) $(CET_DFLAGS)
+
+# Flags for other kinds of sources
+AM_CFLAGS=$(CET_FLAGS)
 
 # Install all D files
 ALL_PHOBOS_INSTALL_DSOURCES = $(PHOBOS_DSOURCES)
diff --git a/libphobos/src/Makefile.in b/libphobos/src/Makefile.in
index dc5f4f5ca57..4a0612a613b 100644
--- a/libphobos/src/Makefile.in
+++ b/libphobos/src/Makefile.in
@@ -323,6 +323,7 @@ CC = @CC@
 CCAS = @CCAS@
 CCASFLAGS = @CCASFLAGS@
 CC_FOR_BUILD = @CC_FOR_BUILD@
+CET_DFLAGS = @CET_DFLAGS@
 CET_FLAGS = @CET_FLAGS@
 CFLAGS = @CFLAGS@
 CFLAGS_FOR_BUILD = @CFLAGS_FOR_BUILD@
@@ -332,7 +333,6 @@ CPPFLAGS = @CPPFLAGS@
 CYGPATH_W = @CYGPATH_W@
 DCFG_ARM_EABI_UNWINDER = @DCFG_ARM_EABI_UNWINDER@
 DCFG_DLPI_TLS_MODID = @DCFG_DLPI_TLS_MODID@
-DCFG_ENABLE_CET = @DCFG_ENABLE_CET@
 DCFG_HAVE_64BIT_ATOMICS = @DCFG_HAVE_64BIT_ATOMICS@
 DCFG_HAVE_ATOMIC_BUILTINS = @DCFG_HAVE_ATOMIC_BUILTINS@
 DCFG_HAVE_LIBATOMIC = @DCFG_HAVE_LIBATOMIC@
@@ -477,9 +477,12 @@ D_EXTRA_DFLAGS = -nostdinc -I $(srcdir) \
 # D flags for compilation
 AM_DFLAGS = \
 	$(phobos_compiler_pic_flag) \
-	$(WARN_DFLAGS) $(CHECKING_DFLAGS)
+	$(WARN_DFLAGS) $(CHECKING_DFLAGS) $(CET_DFLAGS)
 
 
+# Flags for other kinds of sources
+AM_CFLAGS = $(CET_FLAGS)
+
 # Install all D files
 ALL_PHOBOS_INSTALL_DSOURCES = $(PHOBOS_DSOURCES)
 
diff --git a/libphobos/testsuite/Makefile.in b/libphobos/testsuite/Makefile.in
index 5a4c0317509..2f6911d4d47 100644
--- a/libphobos/testsuite/Makefile.in
+++ b/libphobos/testsuite/Makefile.in
@@ -151,6 +151,7 @@ CC = @CC@
 CCAS = @CCAS@
 CCASFLAGS = @CCASFLAGS@
 CC_FOR_BUILD = @CC_FOR_BUILD@
+CET_DFLAGS = @CET_DFLAGS@
 CET_FLAGS = @CET_FLAGS@
 CFLAGS = @CFLAGS@
 CFLAGS_FOR_BUILD = @CFLAGS_FOR_BUILD@
@@ -160,7 +161,6 @@ CPPFLAGS = @CPPFLAGS@
 CYGPATH_W = @CYGPATH_W@
 DCFG_ARM_EABI_UNWINDER = @DCFG_ARM_EABI_UNWINDER@
 DCFG_DLPI_TLS_MODID = @DCFG_DLPI_TLS_MODID@
-DCFG_ENABLE_CET = @DCFG_ENABLE_CET@
 DCFG_HAVE_64BIT_ATOMICS = @DCFG_HAVE_64BIT_ATOMICS@
 DCFG_HAVE_ATOMIC_BUILTINS = @DCFG_HAVE_ATOMIC_BUILTINS@
 DCFG_HAVE_LIBATOMIC = @DCFG_HAVE_LIBATOMIC@
diff --git a/libphobos/testsuite/testsuite_flags.in b/libphobos/testsuite/testsuite_flags.in
index 14b67950607..6a2d79f0cd2 100755
--- a/libphobos/testsuite/testsuite_flags.in
+++ b/libphobos/testsuite/testsuite_flags.in
@@ -28,7 +28,7 @@ case ${query} in
       ;;
     --gdcflags)
       GDCFLAGS_default="-fmessage-length=0 -fno-show-column"
-      GDCFLAGS_config="@WARN_DFLAGS@ @GDCFLAGS@ -fno-release -funittest"
+      GDCFLAGS_config="@WARN_DFLAGS@ @GDCFLAGS@ @CET_DFLAGS@ -fno-release -funittest"
       echo ${GDCFLAGS_default} ${GDCFLAGS_config}
       ;;
     --gdcpaths)