diff --git a/DESCRIPTION b/DESCRIPTION
index 3ca2e75a5..c1120d4a6 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: ergm
-Version: 4.7-7448
-Date: 2024-10-14
+Version: 4.7-7451
+Date: 2024-11-01
 Title: Fit, Simulate and Diagnose Exponential-Family Models for Networks
 Authors@R: c(
              person(c("Mark", "S."), "Handcock", role=c("aut"), email="handcock@stat.ucla.edu"),
diff --git a/inst/include/ergm_model.h b/inst/include/ergm_model.h
index f42dd98dc..c796dd84c 100644
--- a/inst/include/ergm_model.h
+++ b/inst/include/ergm_model.h
@@ -103,6 +103,8 @@ int GetIndexForAttrValue(int value);
 
 /* *** don't forget tail-> head, so this function accepts toggletail first, not togglehead  */
 
+void ChangeStatsDo(unsigned int ntoggles, Vertex *tails, Vertex *heads, Network *nwp, Model *m);
+void ChangeStatsUndo(unsigned int ntoggles, Vertex *tails, Vertex *heads, Network *nwp, Model *m);
 void ChangeStats(unsigned int ntoggles, Vertex *tails, Vertex *heads, Network *nwp, Model *m);
 void ChangeStats1(Vertex tail, Vertex head, Network *nwp, Model *m, Rboolean edgestate);
 void ZStats(Network *nwp, Model *m, Rboolean skip_s);
diff --git a/inst/include/ergm_wtmodel.h b/inst/include/ergm_wtmodel.h
index ba271edf3..bdaebaea1 100644
--- a/inst/include/ergm_wtmodel.h
+++ b/inst/include/ergm_wtmodel.h
@@ -98,6 +98,8 @@ void WtModelDestroy(WtNetwork *nwp, WtModel *m);
    total numbers of terms, parameters, and statistics along with a pointer
    to an array of WtModelTerm structures.  */
 
+void WtChangeStatsDo(unsigned int ntoggles, Vertex *tails, Vertex *heads, double *weights, WtNetwork *nwp, WtModel *m);
+void WtChangeStatsUndo(unsigned int ntoggles, Vertex *tails, Vertex *heads, double *weights, WtNetwork *nwp, WtModel *m);
 void WtChangeStats(unsigned int ntoggles, Vertex *tails, Vertex *heads, double *weights, WtNetwork *nwp, WtModel *m);
 void WtChangeStats1(Vertex tail, Vertex head, double weight, WtNetwork *nwp, WtModel *m, double edgestate);
 void WtZStats(WtNetwork *nwp, WtModel *m, Rboolean skip_s);
diff --git a/src/MCMC.c.template.do_not_include_directly.h b/src/MCMC.c.template.do_not_include_directly.h
index c533f3a83..ab92606c5 100644
--- a/src/MCMC.c.template.do_not_include_directly.h
+++ b/src/MCMC.c.template.do_not_include_directly.h
@@ -229,7 +229,7 @@ MCMCStatus DISPATCH_MetropolisHastings (DISPATCH_ErgmState *s,
 
     /* Calculate change statistics,
        remembering that tail -> head */
-    PROP_CHANGESTATS;
+    PROP_CHANGESTATS_DO;
 
     if(verbose>=5) print_vector("stat diff", m->workspace, m->n_stats);
 
@@ -251,8 +251,8 @@ MCMCStatus DISPATCH_MetropolisHastings (DISPATCH_ErgmState *s,
 	Rprintf("Accepted.\n");
       }
 
-      /* Make proposed toggles (updating timestamps--i.e., for real this time) */
-      for(unsigned int i=0; i < MHp->ntoggles; i++) PROP_COMMIT;
+      /* Make the last (or sole) toggle. */
+      PROP_FINISH;
       /* record network statistics for posterity */
       addonto(networkstatistics, m->workspace, m->n_stats);
       taken++;
@@ -260,6 +260,8 @@ MCMCStatus DISPATCH_MetropolisHastings (DISPATCH_ErgmState *s,
       if(verbose>=5){
 	Rprintf("Rejected.\n");
       }
+
+      PROP_CHANGESTATS_UNDO;
     }
   }
 
diff --git a/src/ergm_type_defs_common.h b/src/ergm_type_defs_common.h
index a5ac8d05e..a71db3e5e 100644
--- a/src/ergm_type_defs_common.h
+++ b/src/ergm_type_defs_common.h
@@ -9,7 +9,10 @@
  */
 #define PROP_PRINT Rprintf("  (%d, %d)  ", MHp->toggletail[i], MHp->togglehead[i])
 #define PROP_CHANGESTATS ChangeStats(MHp->ntoggles, MHp->toggletail, MHp->togglehead, nwp, m)
+#define PROP_CHANGESTATS_DO ChangeStatsDo(MHp->ntoggles, MHp->toggletail, MHp->togglehead, nwp, m)
+#define PROP_CHANGESTATS_UNDO ChangeStatsUndo(MHp->ntoggles, MHp->toggletail, MHp->togglehead, nwp, m)
 #define PROP_COMMIT ToggleEdge(MHp->toggletail[i], MHp->togglehead[i], nwp)
+#define PROP_FINISH ToggleEdge(MHp->toggletail[MHp->ntoggles-1], MHp->togglehead[MHp->ntoggles-1], nwp)
 #define DISPATCH_ErgmState ErgmState
 #define DISPATCH_ErgmStateInit ErgmStateInit
 #define DISPATCH_Model Model
diff --git a/src/ergm_wttype_defs_common.h b/src/ergm_wttype_defs_common.h
index 20aa028ab..364fbd6cd 100644
--- a/src/ergm_wttype_defs_common.h
+++ b/src/ergm_wttype_defs_common.h
@@ -9,7 +9,10 @@
  */
 #define PROP_PRINT Rprintf("  (%d, %d) -> %f  ", MHp->toggletail[i], MHp->togglehead[i], MHp->toggleweight[i])
 #define PROP_CHANGESTATS WtChangeStats(MHp->ntoggles, MHp->toggletail, MHp->togglehead, MHp->toggleweight, nwp, m)
+#define PROP_CHANGESTATS_DO WtChangeStatsDo(MHp->ntoggles, MHp->toggletail, MHp->togglehead, MHp->toggleweight, nwp, m)
+#define PROP_CHANGESTATS_UNDO WtChangeStatsUndo(MHp->ntoggles, MHp->toggletail, MHp->togglehead, MHp->toggleweight, nwp, m)
 #define PROP_COMMIT WtSetEdge(MHp->toggletail[i], MHp->togglehead[i], MHp->toggleweight[i], nwp)
+#define PROP_FINISH WtSetEdge(MHp->toggletail[MHp->ntoggles-1], MHp->togglehead[MHp->ntoggles-1], MHp->toggleweight[MHp->ntoggles-1], nwp)
 #define DISPATCH_ErgmState WtErgmState
 #define DISPATCH_ErgmStateInit WtErgmStateInit
 #define DISPATCH_Model WtModel
diff --git a/src/model.c b/src/model.c
index 3d8501152..084dc6fab 100644
--- a/src/model.c
+++ b/src/model.c
@@ -313,13 +313,8 @@ Model* ModelInitialize(SEXP mR, SEXP ext_state, Network *nwp, Rboolean noinit_s)
   return m;
 }
 
-/*
-  ChangeStats
-  A helper's helper function to compute change statistics.
-  The vector of changes is written to m->workspace.
-*/
-void ChangeStats(unsigned int ntoggles, Vertex *tails, Vertex *heads,
-				 Network *nwp, Model *m){
+void ChangeStatsDo(unsigned int ntoggles, Vertex *tails, Vertex *heads,
+                   Network *nwp, Model *m){
   memset(m->workspace, 0, m->n_stats*sizeof(double)); /* Zero all change stats. */ 
 
   /* Make a pass through terms with d_functions. */
@@ -364,15 +359,30 @@ void ChangeStats(unsigned int ntoggles, Vertex *tails, Vertex *heads,
       TOGGLE_KNOWN(tails[toggle],heads[toggle], edgestate);
     }
   }
-  /* Undo previous storage updates and toggles */
+}
+
+void ChangeStatsUndo(unsigned int ntoggles, Vertex *tails, Vertex *heads,
+                     Network *nwp, Model *m){
+  int toggle = ntoggles;
   UNDO_PREVIOUS(toggle){
     TOGGLE(tails[toggle],heads[toggle]);
   }
 }
 
+/*
+  ChangeStats
+  A helper's helper function to compute change statistics.
+  The vector of changes is written to m->workspace.
+*/
+void ChangeStats(unsigned int ntoggles, Vertex *tails, Vertex *heads,
+                 Network *nwp, Model *m){
+  ChangeStatsDo(ntoggles, tails, heads, nwp, m);
+  ChangeStatsUndo(ntoggles, tails, heads, nwp, m);
+}
+
 /*
   ChangeStats1
-  A simplified version of WtChangeStats for exactly one change.
+  A simplified version of ChangeStats for exactly one change.
 */
 void ChangeStats1(Vertex tail, Vertex head,
                   Network *nwp, Model *m, Rboolean edgestate){
diff --git a/src/wtmodel.c b/src/wtmodel.c
index c29300879..47c6ddb74 100644
--- a/src/wtmodel.c
+++ b/src/wtmodel.c
@@ -315,13 +315,8 @@ WtModel* WtModelInitialize (SEXP mR, SEXP ext_state, WtNetwork *nwp, Rboolean no
   return m;
 }
 
-/*
-  WtChangeStats
-  A helper's helper function to compute change statistics.
-  The vector of changes is written to m->workspace.
-*/
-void WtChangeStats(unsigned int ntoggles, Vertex *tails, Vertex *heads, double *weights,
-				 WtNetwork *nwp, WtModel *m){
+void WtChangeStatsDo(unsigned int ntoggles, Vertex *tails, Vertex *heads, double *weights,
+                   WtNetwork *nwp, WtModel *m){
   memset(m->workspace, 0, m->n_stats*sizeof(double)); /* Zero all change stats. */ 
 
   /* Make a pass through terms with d_functions. */
@@ -365,7 +360,11 @@ void WtChangeStats(unsigned int ntoggles, Vertex *tails, Vertex *heads, double *
       SETWT_WITH_BACKUP();
     }
   }
-  /* Undo previous storage updates and toggles */
+}
+
+
+void WtChangeStatsUndo(unsigned int ntoggles, Vertex *tails, Vertex *heads, double *weights,
+                       WtNetwork *nwp, WtModel *m){
   UNDO_PREVIOUS{
     GETOLDTOGGLEINFO();
     SETWT(TAIL,HEAD,weights[TOGGLEIND]);
@@ -373,6 +372,18 @@ void WtChangeStats(unsigned int ntoggles, Vertex *tails, Vertex *heads, double *
   }
 }
 
+
+/*
+  WtChangeStats
+  A helper's helper function to compute change statistics.
+  The vector of changes is written to m->workspace.
+*/
+void WtChangeStats(unsigned int ntoggles, Vertex *tails, Vertex *heads, double *weights,
+				 WtNetwork *nwp, WtModel *m){
+  WtChangeStatsDo(ntoggles, tails, heads, weights, nwp, m);
+  WtChangeStatsUndo(ntoggles, tails, heads, weights, nwp, m);
+}
+
 /*
   WtChangeStats1
   A simplified version of WtChangeStats for exactly one change.