diff --git a/fast-import.c b/fast-import.c
index ee7258037a..1f9160b645 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -1763,7 +1763,6 @@ static int read_next_command(void)
 		} else {
 			struct recent_command *rc;
 
-			strbuf_detach(&command_buf, NULL);
 			stdin_eof = strbuf_getline_lf(&command_buf, stdin);
 			if (stdin_eof)
 				return EOF;
@@ -1784,7 +1783,7 @@ static int read_next_command(void)
 				free(rc->buf);
 			}
 
-			rc->buf = command_buf.buf;
+			rc->buf = xstrdup(command_buf.buf);
 			rc->prev = cmd_tail;
 			rc->next = cmd_hist.prev;
 			rc->prev->next = rc;
@@ -1833,7 +1832,6 @@ static int parse_data(struct strbuf *sb, uintmax_t limit, uintmax_t *len_res)
 		char *term = xstrdup(data);
 		size_t term_len = command_buf.len - (data - command_buf.buf);
 
-		strbuf_detach(&command_buf, NULL);
 		for (;;) {
 			if (strbuf_getline_lf(&command_buf, stdin) == EOF)
 				die("EOF in data (terminator '%s' not found)", term);
diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index cf66b40ebc..141b7fa35e 100755
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -3314,11 +3314,6 @@ test_expect_success 'X: handling encoding' '
 
 	printf "Pi: \360\nCOMMIT\n" >>input &&
 
-	for i in $(test_seq 100)
-	do
-		echo "M 644 $EMPTY_BLOB file-$i"
-	done >>input &&
-
 	git fast-import <input &&
 	git cat-file -p encoding | grep $(printf "\360") &&
 	git log -1 --format=%B encoding | grep $(printf "\317\200")