diff --git a/coregrind/m_syswrap/priv_syswrap-linux.h b/coregrind/m_syswrap/priv_syswrap-linux.h
index 6c871be81..addb5bc79 100644
--- a/coregrind/m_syswrap/priv_syswrap-linux.h
+++ b/coregrind/m_syswrap/priv_syswrap-linux.h
@@ -34,7 +34,7 @@
 /* requires #include "priv_types_n_macros.h" */
 
 // Clone-related functions
-extern Int  ML_(start_thread_NORETURN) ( void* arg );
+extern Word ML_(start_thread_NORETURN) ( void* arg );
 extern Addr ML_(allocstack)            ( ThreadId tid );
 extern void ML_(call_on_new_stack_0_1) ( Addr stack, Addr retaddr,
 			                 void (*f)(Word), Word arg1 );
diff --git a/coregrind/m_syswrap/syswrap-amd64-linux.c b/coregrind/m_syswrap/syswrap-amd64-linux.c
index 257820d39..84923cc0f 100644
--- a/coregrind/m_syswrap/syswrap-amd64-linux.c
+++ b/coregrind/m_syswrap/syswrap-amd64-linux.c
@@ -126,7 +126,7 @@ asm(
 #define __NR_EXIT         VG_STRINGIFY(__NR_exit)
 
 extern
-Long do_syscall_clone_amd64_linux ( Long (*fn)(void *), 
+Long do_syscall_clone_amd64_linux ( Word (*fn)(void *), 
                                     void* stack, 
                                     Long  flags, 
                                     void* arg,
diff --git a/coregrind/m_syswrap/syswrap-linux.c b/coregrind/m_syswrap/syswrap-linux.c
index e1615c533..da0546854 100644
--- a/coregrind/m_syswrap/syswrap-linux.c
+++ b/coregrind/m_syswrap/syswrap-linux.c
@@ -198,7 +198,7 @@ static void run_a_thread_NORETURN ( Word tidW )
    vg_assert(0);
 }
 
-Int ML_(start_thread_NORETURN) ( void* arg )
+Word ML_(start_thread_NORETURN) ( void* arg )
 {
    ThreadState* tst = (ThreadState*)arg;
    ThreadId     tid = tst->tid;
diff --git a/coregrind/m_syswrap/syswrap-ppc32-linux.c b/coregrind/m_syswrap/syswrap-ppc32-linux.c
index e171a5908..f88492757 100644
--- a/coregrind/m_syswrap/syswrap-ppc32-linux.c
+++ b/coregrind/m_syswrap/syswrap-ppc32-linux.c
@@ -143,7 +143,7 @@ asm(
 #define __NR_EXIT         VG_STRINGIFY(__NR_exit)
 
 extern
-ULong do_syscall_clone_ppc32_linux ( Int (*fn)(void *), 
+ULong do_syscall_clone_ppc32_linux ( Word (*fn)(void *), 
                                      void* stack, 
                                      Int   flags, 
                                      void* arg,
diff --git a/coregrind/m_syswrap/syswrap-x86-linux.c b/coregrind/m_syswrap/syswrap-x86-linux.c
index f5c00ac59..d9b058394 100644
--- a/coregrind/m_syswrap/syswrap-x86-linux.c
+++ b/coregrind/m_syswrap/syswrap-x86-linux.c
@@ -128,7 +128,7 @@ asm(
 #define __NR_EXIT         VG_STRINGIFY(__NR_exit)
 
 extern
-Int do_syscall_clone_x86_linux ( Int (*fn)(void *), 
+Int do_syscall_clone_x86_linux ( Word (*fn)(void *), 
                                  void* stack, 
                                  Int   flags, 
                                  void* arg,