diff --git bin/sh/miscbltin.c bin/sh/miscbltin.c
index 9d0280bb548a..8de8942f4fa5 100644
--- bin/sh/miscbltin.c
+++ bin/sh/miscbltin.c
@@ -162,6 +162,7 @@ readcmd(int argc __unused, char **argv __unused)
 	int is_ifs;
 	int saveall = 0;
 	ptrdiff_t lastnonifs, lastnonifsws;
+	struct timespec tnow, tend;
 	struct timeval tv;
 	char *tvptr;
 	fd_set ifds;
@@ -187,19 +188,20 @@ readcmd(int argc __unused, char **argv __unused)
 			tv.tv_sec = strtol(shoptarg, &tvptr, 0);
 			if (tvptr == shoptarg)
 				error("timeout value");
-			switch(*tvptr) {
-			case 0:
+			switch (*tvptr) {
 			case 's':
+				tvptr++;
 				break;
 			case 'h':
 				tv.tv_sec *= 60;
 				/* FALLTHROUGH */
 			case 'm':
 				tv.tv_sec *= 60;
+				tvptr++;
 				break;
-			default:
-				error("timeout unit");
 			}
+			if (*tvptr != '\0')
+				error("timeout unit");
 			break;
 		}
 	}
@@ -216,16 +218,36 @@ readcmd(int argc __unused, char **argv __unused)
 		/*
 		 * Wait for something to become available.
 		 */
+		status = sig = 0;
 		FD_ZERO(&ifds);
 		FD_SET(0, &ifds);
-		status = select(1, &ifds, NULL, NULL, &tv);
+		if (tv.tv_sec == 0) {
+			status = select(1, &ifds, NULL, NULL, &tv);
+			sig = pendingsig;
+		} else {
+			clock_gettime(CLOCK_UPTIME, &tnow);
+			tend = tnow;
+			tend.tv_sec += tv.tv_sec;
+			do {
+				status = select(1, &ifds, NULL, NULL, &tv);
+				if (status == 0 || status == 1 ||
+				    (status < 0 && (sig = pendingsig) != 0))
+					break;
+				tv.tv_sec = tend.tv_sec - tnow.tv_sec;
+				tv.tv_usec = (tend.tv_nsec - tnow.tv_nsec) / 1000;
+				if (tv.tv_usec < 0) {
+					tv.tv_sec--;
+					tv.tv_usec -= 1000000;
+				}
+				clock_gettime(CLOCK_UPTIME, &tnow);
+			} while (timespeccmp(&tnow, &tend, <));
+		}
 		/*
 		 * If there's nothing ready, return an error.
 		 */
 		if (status <= 0) {
 			while (*ap != NULL)
 				setvar(*ap++, "", 0);
-			sig = pendingsig;
 			return (128 + (sig != 0 ? sig : SIGALRM));
 		}
 	}