diff --git a/mps/code/mpm.h b/mps/code/mpm.h
index 165c7485e37..58fb4da6a31 100644
--- a/mps/code/mpm.h
+++ b/mps/code/mpm.h
@@ -936,14 +936,14 @@ extern Res RootCreateTableMasked(Root *rootReturn, Arena arena,
                                  Word mask);
 extern Res RootCreateReg(Root *rootReturn, Arena arena,
                            Rank rank, Thread thread,
-                           RootScanRegMethod scan,
+                           mps_reg_scan_t scan,
                            void *p, size_t s);
 extern Res RootCreateFmt(Root *rootReturn, Arena arena,
                            Rank rank, RootMode mode,
                            FormatScanMethod scan,
                            Addr base, Addr limit);
 extern Res RootCreateFun(Root *rootReturn, Arena arena,
-                        Rank rank, RootScanMethod scan,
+                        Rank rank, mps_root_scan_t scan,
                         void *p, size_t s);
 extern void RootDestroy(Root root);
 extern Bool RootModeCheck(RootMode mode);
diff --git a/mps/code/mpmtypes.h b/mps/code/mpmtypes.h
index b1853178cbb..12d23e39989 100644
--- a/mps/code/mpmtypes.h
+++ b/mps/code/mpmtypes.h
@@ -96,7 +96,7 @@ typedef struct mps_arena_s *Arena;      /* <design/arena/> */
 typedef struct GlobalsStruct *Globals;  /* <design/arena/> */
 typedef struct VMStruct *VM;            /* <code/vm.c>* */
 typedef struct RootStruct *Root;        /* <code/root.c> */
-typedef struct ThreadStruct *Thread;    /* <code/th.c>* */
+typedef struct mps_thr_s *Thread;       /* <code/th.c>* */
 typedef struct MutatorFaultContextStruct
         *MutatorFaultContext;           /* <design/prot/> */
 typedef struct PoolDebugMixinStruct *PoolDebugMixin;
@@ -255,14 +255,6 @@ typedef void (*FormatPadMethod)(Addr base, Size size);
 typedef Addr (*FormatClassMethod)(Addr object);
 
 
-/* Root*Method -- see design.mps.root-interface */
-/* .root-methods: These methods must match those defined in the */
-/* MPS C Interface.  (See <code/mps.h#root-methods>.) */
-
-typedef Res (*RootScanMethod)(mps_ss_t ss, void *p, size_t s);
-typedef Res (*RootScanRegMethod)(mps_ss_t ss, Thread thread, void *p, size_t s);
-
-
 /* CONSTANTS */
 
 
diff --git a/mps/code/mps.h b/mps/code/mps.h
index 469639b6c6d..945d43cc13b 100644
--- a/mps/code/mps.h
+++ b/mps/code/mps.h
@@ -178,6 +178,7 @@ typedef struct mps_ld_s {       /* location dependency descriptor */
 
 
 /* Format and Root Method Types */
+/* see design.mps.root-interface */
 /* .fmt-methods: Keep in sync with <code/mpmtypes.h#fmt-methods> */
 /* .root-methods: Keep in sync with <code/mpmtypes.h#root-methods> */
 
diff --git a/mps/code/mpsi.c b/mps/code/mpsi.c
index 240861f8dad..c620cad18dd 100644
--- a/mps/code/mpsi.c
+++ b/mps/code/mpsi.c
@@ -1194,8 +1194,7 @@ mps_res_t mps_root_create(mps_root_t *mps_root_o, mps_arena_t arena,
   AVER(mps_rm == (mps_rm_t)0);
 
   /* See .root-mode. */
-  res = RootCreateFun(&root, arena, rank,
-                      (RootScanMethod)mps_root_scan, p, s);
+  res = RootCreateFun(&root, arena, rank, mps_root_scan, p, s);
 
   ArenaLeave(arena);
 
@@ -1308,8 +1307,7 @@ mps_res_t mps_root_create_reg(mps_root_t *mps_root_o, mps_arena_t arena,
 
   /* See .root-mode. */
   res = RootCreateReg(&root, arena, rank, thread,
-                      (RootScanRegMethod)mps_reg_scan,
-                      reg_scan_p, mps_size);
+                      mps_reg_scan, reg_scan_p, mps_size);
 
   ArenaLeave(arena);
 
diff --git a/mps/code/root.c b/mps/code/root.c
index 9ce385a124c..c94217c04ad 100644
--- a/mps/code/root.c
+++ b/mps/code/root.c
@@ -33,7 +33,7 @@ typedef struct RootStruct {
   RootVar var;                  /* union discriminator */
   union RootUnion {
     struct {
-      RootScanMethod scan;      /* the function which does the scanning */
+      mps_root_scan_t scan;     /* the function which does the scanning */
       void *p;                  /* environment for scan */
       size_t s;                 /* environment for scan */
     } fun;
@@ -47,7 +47,7 @@ typedef struct RootStruct {
       Word mask;                /* tag mask for scanning */
     } tableMasked;
     struct {
-      RootScanRegMethod scan;   /* function for scanning registers */
+      mps_reg_scan_t scan;      /* function for scanning registers */
       Thread thread;            /* passed to scan */
       void *p;                  /* passed to scan */
       size_t s;                 /* passed to scan */
@@ -296,7 +296,7 @@ Res RootCreateTableMasked(Root *rootReturn, Arena arena,
 
 Res RootCreateReg(Root *rootReturn, Arena arena,
                   Rank rank, Thread thread,
-                  RootScanRegMethod scan, void *p, size_t s)
+                  mps_reg_scan_t scan, void *p, size_t s)
 {
   union RootUnion theUnion;
 
@@ -336,7 +336,7 @@ Res RootCreateFmt(Root *rootReturn, Arena arena,
 }
 
 Res RootCreateFun(Root *rootReturn, Arena arena, Rank rank,
-                  RootScanMethod scan, void *p, size_t s)
+                  mps_root_scan_t scan, void *p, size_t s)
 {
   union RootUnion theUnion;
 
diff --git a/mps/code/than.c b/mps/code/than.c
index 96553c7cd75..752ef3ed64c 100644
--- a/mps/code/than.c
+++ b/mps/code/than.c
@@ -17,7 +17,7 @@
 SRCID(than, "$Id$");
 
 
-typedef struct ThreadStruct {   /* ANSI fake thread structure */
+typedef struct mps_thr_s {      /* ANSI fake thread structure */
   Sig sig;                      /* <design/sig/> */
   Serial serial;                /* from arena->threadSerial */
   Arena arena;                  /* owning arena */
diff --git a/mps/code/thix.c b/mps/code/thix.c
index 5089f33f56e..b792cd96783 100644
--- a/mps/code/thix.c
+++ b/mps/code/thix.c
@@ -43,7 +43,7 @@ SRCID(thix, "$Id$");
 
 /* ThreadStruct -- thread desriptor */
 
-typedef struct ThreadStruct {    /* PThreads thread structure */
+typedef struct mps_thr_s {       /* PThreads thread structure */
   Sig sig;                       /* <design/sig/> */
   Serial serial;                 /* from arena->threadSerial */
   Arena arena;                   /* owning arena */
diff --git a/mps/code/thw3.h b/mps/code/thw3.h
index b3e67cb319d..7e3cd68e2f1 100644
--- a/mps/code/thw3.h
+++ b/mps/code/thw3.h
@@ -21,7 +21,7 @@
 
 #include "mpswin.h"
 
-typedef struct ThreadStruct {   /* Win32 thread structure */
+typedef struct mps_thr_s {      /* Win32 thread structure */
   Sig sig;                      /* <design/sig/> */
   Serial serial;                /* from arena->threadSerial */
   Arena arena;                  /* owning arena */