Index: usr.bin/sed/defs.h
===================================================================
--- usr.bin/sed/defs.h	(revision 243746)
+++ usr.bin/sed/defs.h	(working copy)
@@ -143,6 +143,7 @@
 	char *space;		/* Current space pointer. */
 	size_t len;		/* Current length. */
 	int deleted;		/* If deleted. */
+	int append_newline;	/* If originally terminated by \n. */
 	char *back;		/* Backing memory. */
 	size_t blen;		/* Backing memory length. */
 } SPACE;
Index: usr.bin/sed/main.c
===================================================================
--- usr.bin/sed/main.c	(revision 243746)
+++ usr.bin/sed/main.c	(working copy)
@@ -431,8 +431,12 @@
 	p = fgetln(infile, &len);
 	if (ferror(infile))
 		errx(1, "%s: %s", fname, strerror(errno ? errno : EIO));
-	if (len != 0 && p[len - 1] == '\n')
+	if (len != 0 && p[len - 1] == '\n') {
+		sp->append_newline = 1;
 		len--;
+	} else {
+		sp->append_newline = 0;
+	}
 	cspace(sp, p, len, spflag);
 
 	linenum++;
Index: usr.bin/sed/process.c
===================================================================
--- usr.bin/sed/process.c	(revision 243746)
+++ usr.bin/sed/process.c	(working copy)
@@ -63,6 +63,7 @@
 #define	pd		PS.deleted
 #define	ps		PS.space
 #define	psl		PS.len
+#define	panl		PS.append_newline
 #define	hs		HS.space
 #define	hsl		HS.len
 
@@ -85,7 +86,10 @@
 size_t maxnsub;
 regmatch_t *match;
 
-#define OUT() do {fwrite(ps, 1, psl, outfile); fputc('\n', outfile);} while (0)
+#define OUT() do {							\
+	fwrite(ps, 1, psl, outfile);					\
+	if (panl) fputc('\n', outfile);					\
+} while (0)
 
 void
 process(void)
@@ -94,6 +98,7 @@
 	SPACE tspace;
 	size_t oldpsl = 0;
 	char *p;
+	int oldpanl;
 
 	p = NULL;
 
@@ -190,11 +195,15 @@
 					break;
 				if ((p = memchr(ps, '\n', psl)) != NULL) {
 					oldpsl = psl;
+					oldpanl = panl;
 					psl = p - ps;
+					panl = 0;
 				}
 				OUT();
-				if (p != NULL)
+				if (p != NULL) {
 					psl = oldpsl;
+					panl = oldpanl;
+				}
 				break;
 			case 'q':
 				if (!nflag && !pd)
@@ -244,6 +253,7 @@
 					cspace(&HS, "", 0, REPLACE);
 				tspace = PS;
 				PS = HS;
+				panl = tspace.append_newline;
 				HS = tspace;
 				break;
 			case 'y':
@@ -444,6 +454,7 @@
 	 */
 	tspace = PS;
 	PS = SS;
+	panl = tspace.append_newline;
 	SS = tspace;
 	SS.space = SS.back;
 
@@ -513,6 +524,7 @@
 		/* Swap the translation space and the pattern space. */
 		tmp = PS;
 		PS = YS;
+		panl = tmp.append_newline;
 		YS = tmp;
 		YS.space = YS.back;
 	}