diff --git a/plow/PlowJogs.c b/plow/PlowJogs.c
index b079663e..6f0cc011 100644
--- a/plow/PlowJogs.c
+++ b/plow/PlowJogs.c
@@ -189,12 +189,12 @@ plowProcessJog(edge, area)
      * it returns 1 and aborts.  We must therefore iterate until no more
      * jogs are eliminated.
      */
-    while (plowSrShadowBack(edge->e_pNum, &r, DBSpaceBits,
+    while (plowSrShadowBack(edge->e_pNum, &r, &DBSpaceBits,
 		plowProcessJogFunc, (ClientData) area))
 	/* Nothing */;
 
     /* Scan to next edge between space and material */
-    (void) plowSrShadowBack(edge->e_pNum, &r, DBAllButSpaceBits,
+    (void) plowSrShadowBack(edge->e_pNum, &r, &DBAllButSpaceBits,
 		plowJogPropagateLeft, (ClientData) NULL);
 }
 
@@ -372,7 +372,7 @@ plowProcessJogFunc(edge, area)
 
     ret = 0;
     plowJogEraseList = (LinkedRect *) NULL;
-    if (plowSrShadowBack(newedge.e_pNum, &r, mask,
+    if (plowSrShadowBack(newedge.e_pNum, &r, &mask,
 		plowJogDragLHS, INT2CD(newedge.e_newx - width)) == 0)
     {
 	/* Success: first paint to extend the RHS of the jog */
diff --git a/plow/PlowSearch.c b/plow/PlowSearch.c
index 7105d7b4..4d26d221 100644
--- a/plow/PlowSearch.c
+++ b/plow/PlowSearch.c
@@ -512,16 +512,17 @@ plowShadowInitialRHS(tp, s, bottomLeft)
  */
 
 int
-plowSrShadowBack(pNum, area, okTypes, proc, cdata)
-    int pNum;			/* Plane from plowYankDef to search */
-    Rect *area;			/* Area to search.  Edges coincident with the
+plowSrShadowBack(
+    int pNum,			/* Plane from plowYankDef to search */
+    Rect *area,			/* Area to search.  Edges coincident with the
 				 * left-hand side of this area are not seen;
 				 * they must lie to the right of area->r_xbot.
 				 */
-    TileTypeBitMask okTypes;
-    int (*proc)();		/* Function to apply at each edge */
-    ClientData cdata;		/* Additional argument to pass to (*proc)() */
+    const TileTypeBitMask *okTypesp,
+    int (*proc)(),		/* Function to apply at each edge */
+    ClientData cdata)		/* Additional argument to pass to (*proc)() */
 {
+    TileTypeBitMask okTypes = *okTypesp; /* TTMaskCopy(&okTypes, okTypesp) */
     Plane *plane = plowYankDef->cd_planes[pNum];
     struct shadow s;
     Tile *tp;
diff --git a/plow/PlowTest.c b/plow/PlowTest.c
index 75cf1bf1..373eb3ae 100644
--- a/plow/PlowTest.c
+++ b/plow/PlowTest.c
@@ -226,7 +226,7 @@ PlowTest(w, cmd)
 	    saveDef = plowYankDef;
 	    plowYankDef = def;
 	    (void) plowSrShadowBack(PL_TECHDEPBASE, &editArea,
-			okTypes, plowShowShadow, (ClientData) def);
+			&okTypes, plowShowShadow, (ClientData) def);
 	    plowYankDef = saveDef;
 	    break;
 	case PC_SHADOW:
diff --git a/plow/plowInt.h b/plow/plowInt.h
index ea0afde7..257be582 100644
--- a/plow/plowInt.h
+++ b/plow/plowInt.h
@@ -265,7 +265,7 @@ extern void plowQueueInit();
 extern int  plowSrFinalArea();
 extern void plowSrOutline(int pNum, Point *startPoint, const TileTypeBitMask *insideTypesp, int initialDir, int dirMask, int (*proc)(), ClientData cdata);
 extern int  plowSrShadow(int pNum, Rect *area, const TileTypeBitMask *okTypesp, int (*proc)(), ClientData cdata);
-extern int  plowSrShadowBack();
+extern int  plowSrShadowBack(int pNum, Rect *area, const TileTypeBitMask *okTypesp, int (*proc)(), ClientData cdata);
 extern int  plowSrShadowInitial();
 extern bool plowYankMore();
 extern void PlowRandomTest();