diff --git a/csrc/pf_guts.h b/csrc/pf_guts.h
index 9782e69..1a49647 100644
--- a/csrc/pf_guts.h
+++ b/csrc/pf_guts.h
@@ -54,9 +54,10 @@
 ** FV10 - 20170103 - Added ID_FILE_FLUSH ID_FILE_RENAME ID_FILE_RESIZE
 ** FV11 - 20241226 - Added ID_SLEEP_P, ID_VAR_BYE_CODE, ID_VERSION_CODE
 ** FV12 - 20241227 - Added Long name support, ID_FLAG_SMUDGE, ID_MASK_NAME_SIZE
+** FV13 - 20250120 - Added R0 for UNRAVEL
 */
 
-#define PF_FILE_VERSION (12)   /* Bump this whenever primitives added. */
+#define PF_FILE_VERSION (13)   /* Bump this whenever primitives added. */
 
 #if defined(PF_SUPPORT_LONG_NAMES)
 #define PF_EARLIEST_FILE_VERSION (12)  /* earliest one still compatible */
@@ -323,6 +324,7 @@ enum cforth_primitive_ids
     ID_VERSION_CODE,
     ID_FLAG_SMUDGE,
     ID_MASK_NAME_SIZE,
+    ID_R_ZERO,             /* R0 , base of return stack */
 /* If you add a word above here,
 **   1. update PF_FILE_VERSION
 **   2. take away one reserved word below
@@ -331,7 +333,6 @@ enum cforth_primitive_ids
 /* Only reserve space if we are adding FP so that we can detect
 ** unsupported primitives when loading dictionary.
 */
-    ID_RESERVED05,
     ID_RESERVED06,
     ID_RESERVED07,
     ID_RESERVED08,
diff --git a/csrc/pf_inner.c b/csrc/pf_inner.c
index 985c3d5..7ade2d2 100644
--- a/csrc/pf_inner.c
+++ b/csrc/pf_inner.c
@@ -1598,6 +1598,11 @@ DBUG(("XX ah,m,l = 0x%8x,%8x,%8x - qh,l = 0x%8x,%8x\n", ah,am,al, qh,ql ));
             M_DROP;
             endcase;
 
+        case ID_R_ZERO:    /* ( -- rbase , base of return stack ) */
+            PUSH_TOS;
+            TOS = (cell_t)gCurrentTask->td_ReturnBase;
+            endcase;
+
         case ID_ROLL: /* ( xu xu-1 xu-1 ... x0 u -- xu-1 xu-1 ... x0 xu ) */
             {
                 cell_t ri;
diff --git a/csrc/pfcompil.c b/csrc/pfcompil.c
index b9c8b8b..87ba056 100644
--- a/csrc/pfcompil.c
+++ b/csrc/pfcompil.c
@@ -337,6 +337,7 @@ PForthDictionary pfBuildDictionary( cell_t HeaderSize, cell_t CodeSize )
     CreateDicEntryC( ID_R_FROM, "R>",  0 );
     CreateDicEntryC( ID_RP_FETCH, "RP@",  0 );
     CreateDicEntryC( ID_RP_STORE, "RP!",  0 );
+    CreateDicEntryC( ID_R_ZERO, "R0",  0 );
     CreateDicEntryC( ID_SEMICOLON, ";",  FLAG_IMMEDIATE );
     CreateDicEntryC( ID_SP_FETCH, "SP@",  0 );
     CreateDicEntryC( ID_SP_STORE, "SP!",  0 );
diff --git a/fth/misc1.fth b/fth/misc1.fth
index 7844df5..676aed5 100644
--- a/fth/misc1.fth
+++ b/fth/misc1.fth
@@ -182,3 +182,19 @@ variable CLOSEST-XT
         UNTIL
     THEN
 ;
+
+: UNRAVEL  ( -- , show names of words on return stack )
+    >newline ." Calling sequence:" cr
+    r0 rp@ - cell /
+    1-     \ skip call into unravel
+    0 max   50 min  \ clip to reasonable range
+    0
+    ?DO  4 spaces
+        rp@ i 2+   \ skip over DO LOOP control and call to UNRAVEL
+        cell* + @
+        dup code> >name ?dup
+        IF id. drop
+        ELSE .
+        THEN cr?
+    LOOP cr
+;