---
 sh.hist.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- sh.hist.c
+++ sh.hist.c	2023-07-21 12:21:55.518480015 +0000
@@ -64,7 +64,7 @@ static	void	hfree	(struct Hist *);
 
 /* #define DEBUG_HIST 1 */
 
-static const int fastMergeErase = 1;
+static int fastMergeErase = 1;
 static unsigned histCount = 0;		/* number elements on history list */
 static int histlen = 0;
 static struct Hist *histTail = NULL;     /* last element on history list */
@@ -1321,6 +1321,7 @@ rechist(Char *xfname, int ref)
 	}
 
 	if (merge) {
+	    fastMergeErase = 0;	/* Was true, now false to merge even with full history list */
 	    jmp_buf_t osetexit;
 	    if (lock) {
 #ifndef WINNT_NATIVE
@@ -1393,7 +1394,7 @@ loadhist(Char *fname, int mflg)
     /* During history merging (enthist sees mflg set), we disable management of
      * Hnum and Href (because fastMergeErase is true).  So now reset all the
      * values based on the final ordering of the history list. */
-    if (mflg) {
+    if (mflg /* && fastMergeErase */) {
 	int n = eventno;
         struct Hist *hp = &Histlist;
         while ((hp = hp->Hnext))
--- tests/history.at
+++ tests/history.at	2023-07-24 07:53:41.471413277 +0000
@@ -218,6 +218,52 @@ dnl savehist) set to 0 instead of 1.
 
 AT_CLEANUP()
 
+AT_SETUP([History merge])
+dnl Check if history merge really works out
+
+AT_DATA([hist-merge.csh],
+[[set histfile=test.history histdup=prev history=(6 "%h TIME %R\n")
+set savehist=(6 merge)
+printf "'%s' %s\n" "$histdup" "$history"
+history -c
+: 1
+: 2
+: 3
+: 4
+: 5
+history -S
+: a
+: b
+: c
+: d
+: e
+history -S
+history -L
+history 6
+]])
+
+AT_CHECK([tcsh -f -q -i < hist-merge.csh], ,
+[> 'prev' 6 %h TIME %R\n
+    24 TIME : b
+    25 TIME : c
+    26 TIME : d
+    27 TIME : e
+    28 TIME history -S
+    29 TIME history 6
+> exit
+],)
+
+dnl In broken case we see the former history instead
+dnl > 'prev' 6 %h TIME %R\n
+dnl    24 TIME : 4
+dnl    25 TIME : 3
+dnl    26 TIME : 2
+dnl    27 TIME : 1
+dnl    28 TIME history -S
+dnl    29 TIME history 6
+dnl > exit
+
+AT_CLEANUP()
 
 dnl
 dnl	History faults