Index: usr.bin/hexdump/conv.c
===================================================================
--- usr.bin/hexdump/conv.c
+++ usr.bin/hexdump/conv.c
@@ -56,6 +56,7 @@
 	size_t clen, oclen;
 	int converr, pad, width;
 	u_char peekbuf[MB_LEN_MAX];
+	u_char *op;
 
 	if (pr->mbleft > 0) {
 		str = "**";
@@ -107,6 +108,15 @@
 		else if (clen == (size_t)-1 || (clen == (size_t)-2 &&
 		    p == peekbuf)) {
 			memset(&pr->mbstate, 0, sizeof(pr->mbstate));
+			if (p == peekbuf) {
+				/*
+				 * We peeked ahead, but that didn't help --
+				 * we either got an illegal sequence or still
+				 * can't complete; restore original character.
+				 */
+				oclen = 0;
+				p = op;
+			}
 			wc = *p;
 			clen = 1;
 			converr = 1;
@@ -116,6 +126,7 @@
 			 * can complete it.
 			 */
 			oclen = bufsize;
+			op = p;
 			bufsize = peek(p = peekbuf, MB_CUR_MAX);
 			goto retry;
 		}
@@ -128,7 +139,7 @@
 		if (!odmode) {
 			*pr->cchar = 'c';
 			(void)printf(pr->fmt, (int)wc);
-		} else {	
+		} else {
 			*pr->cchar = 'C';
 			assert(strcmp(pr->fmt, "%3C") == 0);
 			width = wcwidth(wc);
Index: usr.bin/hexdump/tests/Makefile
===================================================================
--- usr.bin/hexdump/tests/Makefile
+++ usr.bin/hexdump/tests/Makefile
@@ -2,7 +2,7 @@
 
 PACKAGE=	tests
 
-ATF_TESTS_SH=	hexdump_test
+ATF_TESTS_SH=	hexdump_test od_test
 
 ${PACKAGE}FILES+=	d_hexdump_a.in
 ${PACKAGE}FILES+=	d_hexdump_b.in
@@ -27,5 +27,7 @@
 ${PACKAGE}FILES+=	d_hexdump_xflag_a.out
 ${PACKAGE}FILES+=	d_hexdump_xflag_b.out
 ${PACKAGE}FILES+=	d_hexdump_xflag_c.out
+${PACKAGE}FILES+=	d_od_cflag_a.out
+${PACKAGE}FILES+=	d_od_cflag_b.out
 
 .include <bsd.test.mk>
Index: usr.bin/hexdump/tests/d_od_cflag_a.out
===================================================================
--- /dev/null
+++ usr.bin/hexdump/tests/d_od_cflag_a.out
@@ -0,0 +1,3 @@
+0000000    T   e   s   t   T   e   s   t   T   e   s   t   T   e   s 345
+0000020    T   e   s   t 345                                            
+0000025
Index: usr.bin/hexdump/tests/d_od_cflag_b.out
===================================================================
--- /dev/null
+++ usr.bin/hexdump/tests/d_od_cflag_b.out
@@ -0,0 +1,3 @@
+0000000    T   e   s   t   T   e   s   t   T   e   s   t   T   e   s   т
+0000020   **   Т  **   е  **   с  **   т  **                            
+0000031
Index: usr.bin/hexdump/tests/od_test.sh
===================================================================
--- /dev/null
+++ usr.bin/hexdump/tests/od_test.sh
@@ -0,0 +1,45 @@
+#
+# Copyright 2018 The FreeBSD Project
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+# $FreeBSD$
+
+atf_test_case c_flag
+c_flag_head()
+{
+	atf_set "descr" "Verify -c output"
+}
+c_flag_body()
+{
+	printf 'TestTestTestTes\345Test\345' > d_od_cflag.in
+	atf_check -o file:"$(atf_get_srcdir)/d_od_cflag_a.out" \
+	    env LC_CTYPE="en_US.UTF-8" od -c "$(atf_get_srcdir)/d_od_cflag.in"
+	printf 'TestTestTestTesтТест' > d_od_cflag.in
+	atf_check -o file:"$(atf_get_srcdir)/d_od_cflag_b.out" \
+	    env LC_CTYPE="en_US.UTF-8" od -c "$(atf_get_srcdir)/d_od_cflag.in"
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case c_flag
+}