diff --git a/NEWS b/NEWS
index 2b8ebc2fb4ad..52b2441cbb98 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,12 @@ Uppercase BUG_* IDs are shell bug IDs as used by the Modernish shell library.
 - Fixed a bug in 'printf -v' (added on 2021-11-18) where using the %B format
   specifier would overwrite any data already written to the variable.
 
+- [1.1 change] In the ${parameter/pattern/string} search-and-replace
+  expansion, an anchored empty pattern will now match the beginning or the
+  end of the string, so that ${parameter/#/string} will prefix the string to
+  the parameter value and ${parameter/%/string} will append it. This change
+  brings ksh 93u+m/1.1 into line with mksh, bash, yash and zsh.
+
 2023-03-26:
 
 - Fixed an intermittent crash in 'command -x' experienced on some arm/arm64
diff --git a/src/cmd/ksh93/COMPATIBILITY b/src/cmd/ksh93/COMPATIBILITY
index 570574ffb103..907d6eb454ac 100644
--- a/src/cmd/ksh93/COMPATIBILITY
+++ b/src/cmd/ksh93/COMPATIBILITY
@@ -8,6 +8,12 @@ For more details, see the NEWS file and for complete details, see the git log.
 	from the environment. Any script that depends on this will need to
 	be changed to typeset the expected attributes itself.
 
+2.	In the ${parameter/pattern/string} search-and-replace expansion, an
+	anchored empty pattern will now match the beginning or the end of the
+	string, so that ${parameter/#/string} will prefix the string to the
+	parameter value and ${parameter/%/string} will append it. This change
+	brings ksh 93u+m/1.1 into line with mksh, bash, yash and zsh.
+
 ____________________________________________________________________________
 
 		ksh 93u+m vs. ksh 93u+
diff --git a/src/cmd/ksh93/sh/macro.c b/src/cmd/ksh93/sh/macro.c
index e8071f978562..4513be322715 100644
--- a/src/cmd/ksh93/sh/macro.c
+++ b/src/cmd/ksh93/sh/macro.c
@@ -1883,9 +1883,16 @@ static int varsub(Mac_t *mp)
 					oldv = v;
 					nmatch_prev = nmatch;
 					if(c=='%')
-						nmatch=substring(v,tsize,pattern,match,flag&STR_MAXIMAL);
+						nmatch = substring(v, tsize,
+							*pattern ? pattern : "~(E)$",
+							match,
+							flag & STR_MAXIMAL);
 					else
-						nmatch=strngrpmatch(v,vsize,pattern,(ssize_t*)match,elementsof(match)/2,flag|STR_INT);
+						nmatch = strngrpmatch(v, vsize,
+							*pattern ? pattern : "~(E)^",
+							(ssize_t*)match,
+							elementsof(match) / 2,
+							flag | STR_INT);
 					if(nmatch && repstr && !mp->macsub)
 						sh_setmatch(v,vsize,nmatch,match,index++);
 					if(nmatch)
diff --git a/src/cmd/ksh93/tests/substring.sh b/src/cmd/ksh93/tests/substring.sh
index 85d94918df28..8359d86013f7 100755
--- a/src/cmd/ksh93/tests/substring.sh
+++ b/src/cmd/ksh93/tests/substring.sh
@@ -744,5 +744,24 @@ got=${x//~(E:(a)|b)/<\1>}
 exp='<a><>'
 [[ $got == "$exp" ]] || err_exit "back-reference (got $(printf %q "$got"), expected $(printf %q "$exp"))"
 
+# ======
+# On ksh 93u+m/1.1+, anchored empty pattern should match in replacement, e.g. "${@/#/replacement}"
+# https://github.com/ksh93/ksh/issues/558
+case ${.sh.version} in
+*\ 93u+m/1.0.* )
+	;;
+*\ 93u+m/* )
+	set one two three
+	exp=Xone/Xtwo/Xthree
+	got=$(IFS=/; echo "${*/#/X}")
+	[[ $got == "$exp" ]] || err_exit "#-anchored empty pattern vector replacement" \
+		"(got $(printf %q "$got"), expected $(printf %q "$exp"))"
+	exp=oneX/twoX/threeX
+	got=$(IFS=/; echo "${*/%/X}")
+	[[ $got == "$exp" ]] || err_exit "%-anchored empty pattern vector replacement" \
+		"(got $(printf %q "$got"), expected $(printf %q "$exp"))"
+	;;
+esac
+
 # ======
 exit $((Errors<125?Errors:125))