Index: src/bin/dd/dd.c
===================================================================
--- src/bin/dd/dd.c	(revision 238763)
+++ src/bin/dd/dd.c	(working copy)
@@ -116,6 +116,7 @@
 {
 	u_int cnt;
 	struct timeval tv;
+	struct stat sb;
 
 	if (in.name == NULL) {
 		in.name = "stdin";
@@ -138,7 +139,11 @@
 	} else {
 #define	OFLAGS \
     (O_CREAT | (ddflags & (C_SEEK | C_NOTRUNC) ? 0 : O_TRUNC))
-		out.fd = open(out.name, O_RDWR | OFLAGS, DEFFILEMODE);
+
+		if (stat(out.name, &sb) != 0 || !S_ISFIFO(sb.st_mode))
+			out.fd = open(out.name, O_RDWR | OFLAGS, DEFFILEMODE);
+		else
+			out.fd = -1;
 		/*
 		 * May not have read access, so try again with write only.
 		 * Without read we may have a problem if output also does