diff --git a/NEWS b/NEWS
index 638e062a5..4f8d9d91b 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,10 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 
 2021-04-04:
 
+- A bug was fixed that caused a broken prompt display upon redrawing the
+  command line if the last line of the prompt includes an xterm escape
+  sequence that is terminated by $'\a' (the bell character).
+
 - Harden readonly variables. Readonly variables or arrays no longer allow
   attribute changes which would otherwise allow their value to be altered.
   Expanded support for readonly variables within multidimensional arrays.
diff --git a/src/cmd/ksh93/edit/edit.c b/src/cmd/ksh93/edit/edit.c
index b4883ef6b..f6586adf4 100644
--- a/src/cmd/ksh93/edit/edit.c
+++ b/src/cmd/ksh93/edit/edit.c
@@ -651,6 +651,10 @@ void	ed_setup(register Edit_t *ep, int fd, int reedit)
 	ep->e_winsz = ep->e_wsize+2;
 	ep->e_crlf = 1;
 	ep->e_plen = 0;
+	/*
+	 * Prepare e_prompt buffer for use when redrawing the command line.
+	 * Use only the last line of the potentially multi-line prompt.
+	 */
 	pp = ep->e_prompt;
 	ppmax = pp+PRSIZE-1;
 	*pp++ = '\r';
@@ -661,9 +665,40 @@ void	ed_setup(register Edit_t *ep, int fd, int reedit)
 			case ESC:
 			{
 				int skip=0;
+				if(*last == ']')
+				{
+					/*
+					 * Cut out dtterm/xterm Operating System Commands that set window/icon title, etc.
+					 * See: https://invisible-island.net/xterm/ctlseqs/ctlseqs.html
+					 */
+					char *cp = last + 1;
+					while(*cp >= '0' && *cp <= '9')
+						cp++;
+					if(*cp++ == ';')
+					{
+						while(c = *cp++)
+						{
+							if(c == '\a')			/* legacy terminator */
+								break;
+							if(c == ESC && *cp == '\\')	/* recommended terminator */
+							{
+								cp++;
+								break;
+							}
+						}
+						if(!c)
+							break;
+						last = cp;
+						continue;
+					}
+				}
+				/*
+				 * Try to add the length of included escape sequences to qlen
+				 * which is subtracted from the physical length of the prompt.
+				 */
 				ep->e_crlf = 0;
 				if(pp<ppmax)
-					*pp++ = c;
+					*pp++ = ESC;
 				for(n=1; c = *last++; n++)
 				{
 					if(pp < ppmax)
@@ -675,9 +710,11 @@ void	ed_setup(register Edit_t *ep, int fd, int reedit)
 						skip = 0;
 						continue;
 					}
-					if(n>1 && c==';')
+					if(n==3 && (c=='?' || c=='!'))
+						continue;
+					else if(n>1 && c==';')
 						skip = 1;
-					else if(n>2 || (c!= '[' &&  c!= ']'))
+					else if(n>2 || (c!='[' && c!=']' && c!='('))
 						break;
 				}
 				if(c==0 || c==ESC || c=='\r')
diff --git a/src/cmd/ksh93/include/edit.h b/src/cmd/ksh93/include/edit.h
index 1732bbed1..7c80ee9bb 100644
--- a/src/cmd/ksh93/include/edit.h
+++ b/src/cmd/ksh93/include/edit.h
@@ -108,7 +108,7 @@ typedef struct edit
 	char	*e_outptr;	/* pointer to position in output buffer */
 	char	*e_outlast;	/* pointer to end of output buffer */
 	genchar	*e_inbuf;	/* pointer to input buffer */
-	char	*e_prompt;	/* pointer to buffer containing the prompt */
+	char	*e_prompt;	/* pointer to trimmed final line of PS1 prompt, used when redrawing command line */
 	genchar	*e_killbuf;	/* pointer to delete buffer */
 	char	e_search[SEARCHSIZE];	/* search string */
 	genchar	*e_physbuf;	/* temporary workspace buffer */
diff --git a/src/cmd/ksh93/sh.1 b/src/cmd/ksh93/sh.1
index 9c9bf8246..0c6f5c1a5 100644
--- a/src/cmd/ksh93/sh.1
+++ b/src/cmd/ksh93/sh.1
@@ -2122,9 +2122,12 @@ if executing under
 .TP
 .SM
 .B PS1
-The value of this variable is expanded for parameter
-expansion, command substitution, and arithmetic substitution to define the
-primary prompt string which by default is
+Every time a new command line is started on an interactive shell,
+the value of this variable is expanded to resolve
+backslash escaping, parameter expansion, command substitution,
+and arithmetic substitution.
+The result defines the primary prompt string for that command line.
+The default is
 .RB `` "$ \|\|\|" ''.
 The character
 .B !
@@ -2138,6 +2141,12 @@ Two successive occurrences of
 will produce a single
 .B !
 when the prompt string is printed.
+Note that any terminal escape sequences used in the
+.B PS1
+prompt thus need every instance of
+.B !
+in them to be changed to
+.BR !! .
 .TP
 .SM
 .B PS2