diff --git a/valgrind-3.14.0-final_tidyup.patch b/valgrind-3.14.0-final_tidyup.patch
new file mode 100644
index 0000000..f4e7698
--- /dev/null
+++ b/valgrind-3.14.0-final_tidyup.patch
@@ -0,0 +1,59 @@
+commit be7a73004583aab5d4c97cf55276ca58d5b3090b
+Author: Mark Wielaard <mark@klomp.org>
+Date:   Wed Dec 12 14:15:28 2018 +0100
+
+    Mark helper regs defined in final_tidyup before freeres_wrapper call.
+    
+    In final_tidyup we setup the guest to call the freeres_wrapper, which
+    will (possibly) call __gnu_cxx::__freeres() and/or __libc_freeres().
+    
+    In a couple of cases (ppc64be, ppc64le and mips32) this involves setting
+    up one or more helper registers. Since we setup these guest registers
+    we should make sure to mark them as fully defined. Otherwise we might
+    see spurious warnings about undefined value usage if the guest register
+    happened to not be fully defined before.
+    
+    This fixes PR402006.
+
+diff --git a/coregrind/m_main.c b/coregrind/m_main.c
+index 00702fc..22872a2 100644
+--- a/coregrind/m_main.c
++++ b/coregrind/m_main.c
+@@ -2304,22 +2304,35 @@ static void final_tidyup(ThreadId tid)
+                    "Caught __NR_exit; running %s wrapper\n", msgs[to_run - 1]);
+    }
+       
+-   /* set thread context to point to freeres_wrapper */
+-   /* ppc64be-linux note: freeres_wrapper gives us the real
++   /* Set thread context to point to freeres_wrapper.
++      ppc64be-linux note: freeres_wrapper gives us the real
+       function entry point, not a fn descriptor, so can use it
+       directly.  However, we need to set R2 (the toc pointer)
+       appropriately. */
+    VG_(set_IP)(tid, freeres_wrapper);
++
+ #  if defined(VGP_ppc64be_linux)
+    VG_(threads)[tid].arch.vex.guest_GPR2 = r2;
++   VG_TRACK(post_reg_write, Vg_CoreClientReq, tid,
++            offsetof(VexGuestPPC64State, guest_GPR2),
++            sizeof(VG_(threads)[tid].arch.vex.guest_GPR2));
+ #  elif  defined(VGP_ppc64le_linux)
+    /* setting GPR2 but not really needed, GPR12 is needed */
+    VG_(threads)[tid].arch.vex.guest_GPR2  = freeres_wrapper;
++   VG_TRACK(post_reg_write, Vg_CoreClientReq, tid,
++            offsetof(VexGuestPPC64State, guest_GPR2),
++            sizeof(VG_(threads)[tid].arch.vex.guest_GPR2));
+    VG_(threads)[tid].arch.vex.guest_GPR12 = freeres_wrapper;
++   VG_TRACK(post_reg_write, Vg_CoreClientReq, tid,
++            offsetof(VexGuestPPC64State, guest_GPR12),
++            sizeof(VG_(threads)[tid].arch.vex.guest_GPR12));
+ #  endif
+    /* mips-linux note: we need to set t9 */
+ #  if defined(VGP_mips32_linux) || defined(VGP_mips64_linux)
+    VG_(threads)[tid].arch.vex.guest_r25 = freeres_wrapper;
++   VG_TRACK(post_reg_write, Vg_CoreClientReq, tid,
++            offsetof(VexGuestMIPS32State, guest_r25),
++            sizeof(VG_(threads)[tid].arch.vex.guest_r25));
+ #  endif
+ 
+    /* Pass a parameter to freeres_wrapper(). */
diff --git a/valgrind.spec b/valgrind.spec
index 593f97a..caf7447 100644
--- a/valgrind.spec
+++ b/valgrind.spec
@@ -131,6 +131,10 @@ Patch16: valgrind-3.14.0-enable-ppc-Iop_Sar_Shr8.patch
 # KDE#401627 memcheck errors with glibc avx2 optimized wcsncmp
 Patch17: valgrind-3.14.0-wcsncmp.patch
 
+# KDE#402006 mark helper regs defined in final_tidyup before freeres_wrapper
+# Prereq for KDE#386945
+Patch18: valgrind-3.14.0-final_tidyup.patch
+
 %if %{build_multilib}
 # Ensure glibc{,-devel} is installed for both multilib arches
 BuildRequires: /lib/libc.so.6 /usr/lib/libc.so /lib64/libc.so.6 /usr/lib64/libc.so
@@ -280,6 +284,7 @@ Valgrind User Manual for details.
 %patch15 -p1
 %patch16 -p1
 %patch17 -p1
+%patch18 -p1
 
 %build
 CC=gcc
@@ -514,6 +519,9 @@ fi
 %endif
 
 %changelog
+* Wed Dec 12 2018 Mark Wielaard <mjw@fedoraproject.org>
+- Add valgrind-3.14.0-final_tidyup.patch
+
 * Sat Dec  1 2018 Mark Wielaard <mjw@fedoraproject.org> - 3.14.0.5
 - Add valgrind-3.14.0-wcsncmp.patch (#1645971)
 - Replace valgrind-3.14.0-s390x-vec-float-point-{code,test}.patch