diff --git a/NEWS b/NEWS
index 44cc5ed33d35..d55fd75fa36d 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,12 @@ For full details, see the git log at: https://github.com/ksh93/ksh
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2020-07-05:
+
+- In UTF-8 locales, fix corruption of the shell's internal string quoting
+  algorithm (as used by xtrace, 'printf %q', and more) that occurred when
+  the processing of a multibyte character was interrupted.
+
 2020-07-03:
 
 - Backslashes are no longer escaped in the raw Bourne Shell-like editing
diff --git a/src/cmd/ksh93/include/version.h b/src/cmd/ksh93/include/version.h
index 0f0a4fb8c52d..2ee19b9b1b31 100644
--- a/src/cmd/ksh93/include/version.h
+++ b/src/cmd/ksh93/include/version.h
@@ -17,4 +17,4 @@
 *                  David Korn <dgk@research.att.com>                   *
 *                                                                      *
 ***********************************************************************/
-#define SH_RELEASE	"93u+m 2020-07-02"
+#define SH_RELEASE	"93u+m 2020-07-05"
diff --git a/src/cmd/ksh93/sh/string.c b/src/cmd/ksh93/sh/string.c
index 79b37f482209..5eb124b75b23 100644
--- a/src/cmd/ksh93/sh/string.c
+++ b/src/cmd/ksh93/sh/string.c
@@ -336,6 +336,9 @@ char	*sh_fmtq(const char *string)
 	int offset;
 	if(!cp)
 		return((char*)0);
+#if SHOPT_MULTIBYTE
+	mbinit();
+#endif /* SHOPT_MULTIBYTE */
 	offset = staktell();
 	state = ((c= mbchar(cp))==0);
 	if(isaletter(c))
diff --git a/src/cmd/ksh93/tests/builtins.sh b/src/cmd/ksh93/tests/builtins.sh
index 470644be4852..fd093c66bf15 100755
--- a/src/cmd/ksh93/tests/builtins.sh
+++ b/src/cmd/ksh93/tests/builtins.sh
@@ -302,7 +302,23 @@ fi
 if	[[ $(printf '%..*s\n' : abc def) != abc:def ]]
 then	err_exit "printf '%..*s' not working"
 fi
+
+# ======
+# shell-quoting using printf %q (same algorithm used for xtrace and output of 'set', 'trap', ...)
+
 [[ $(printf '%q\n') == '' ]] || err_exit 'printf "%q" with missing arguments'
+
+# the following fails on 2012-08-01 in UTF-8 locales
+expect="'shell-quoted string'"
+actual=$(
+	print -nr $'\303\274' | read -n1 foo  # interrupt processing of 2-byte UTF-8 char after reading 1 byte
+	printf '%q\n' "shell-quoted string"
+)
+LC_CTYPE=POSIX true	    # on buggy ksh, a locale re-init via temp assignment restores correct shellquoting
+[[ $actual == "$expect" ]] || err_exit 'shell-quoting corrupted after interrupted processing of UTF-8 char' \
+				"(expected $expect; got $actual)"
+
+# ======
 # we won't get hit by the one second boundary twice, right?
 expect= actual=
 { expect=$(LC_ALL=C date | sed 's/ GMT / UTC /') && actual=$(LC_ALL=C printf '%T\n' now) && [[ $actual == "$expect" ]]; } ||
diff --git a/src/lib/libast/comp/setlocale.c b/src/lib/libast/comp/setlocale.c
index ba31fe914478..65553f8bb108 100644
--- a/src/lib/libast/comp/setlocale.c
+++ b/src/lib/libast/comp/setlocale.c
@@ -600,6 +600,8 @@ utf8_mbtowc(wchar_t* wp, const char* str, size_t n)
 	register int		c;
 	register wchar_t	w = 0;
 
+	if (!wp && !sp)
+		ast.mb_sync = 0;  /* assume call from mbinit() macro: reset global multibyte sync state */
 	if (!sp || !n)
 		return 0;
 	if ((m = utf8tab[*sp]) > 0)