diff --git a/contrib/hpack/gen-enc.c b/contrib/hpack/gen-enc.c
index dfe47055e..36b132bd7 100644
--- a/contrib/hpack/gen-enc.c
+++ b/contrib/hpack/gen-enc.c
@@ -14,7 +14,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/hpack-tbl.h>
 #include "../../src/hpack-tbl.c"
 
diff --git a/include/common/buffer.h b/include/common/buffer.h
index f7aa2542f..d90b94e8b 100644
--- a/include/common/buffer.h
+++ b/include/common/buffer.h
@@ -29,7 +29,7 @@
 #include <haproxy/api.h>
 #include <common/buf.h>
 #include <common/chunk.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/istbuf.h>
 #include <common/memory.h>
 
diff --git a/include/common/chunk.h b/include/common/chunk.h
index ae7ae8538..d4f9ea23a 100644
--- a/include/common/chunk.h
+++ b/include/common/chunk.h
@@ -27,7 +27,7 @@
 
 #include <haproxy/api.h>
 #include <common/buf.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/memory.h>
 
 
diff --git a/include/common/fcgi.h b/include/common/fcgi.h
index b9a752b92..6d3c6eb19 100644
--- a/include/common/fcgi.h
+++ b/include/common/fcgi.h
@@ -26,7 +26,7 @@
 #include <haproxy/api.h>
 #include <common/standard.h>
 #include <common/buf.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 /* FCGI protocol version */
 #define FCGI_VERSION    0x1
diff --git a/include/common/h1.h b/include/common/h1.h
index 0bc0f4864..f75ee11fb 100644
--- a/include/common/h1.h
+++ b/include/common/h1.h
@@ -26,7 +26,7 @@
 #include <common/buffer.h>
 #include <common/http.h>
 #include <common/http-hdr.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/standard.h>
 
 
diff --git a/include/common/h2.h b/include/common/h2.h
index 5654a7611..32f02060a 100644
--- a/include/common/h2.h
+++ b/include/common/h2.h
@@ -32,7 +32,7 @@
 #include <haproxy/api.h>
 #include <common/http-hdr.h>
 #include <common/htx.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 
 /* indexes of most important pseudo headers can be simplified to an almost
diff --git a/include/common/hpack-enc.h b/include/common/hpack-enc.h
index f204853d7..f766063ff 100644
--- a/include/common/hpack-enc.h
+++ b/include/common/hpack-enc.h
@@ -32,7 +32,7 @@
 #include <haproxy/api.h>
 #include <common/buf.h>
 #include <common/http.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 int hpack_encode_header(struct buffer *out, const struct ist n,
 			const struct ist v);
diff --git a/include/common/hpack-tbl.h b/include/common/hpack-tbl.h
index cde7114af..1d2a8bd5f 100644
--- a/include/common/hpack-tbl.h
+++ b/include/common/hpack-tbl.h
@@ -30,7 +30,7 @@
 #include <stdlib.h>
 #include <haproxy/api.h>
 #include <common/http-hdr.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/memory.h>
 
 /* Dynamic Headers Table, usable for tables up to 4GB long and values of 64kB-1.
diff --git a/include/common/http-hdr.h b/include/common/http-hdr.h
index ffca828d2..77997e33e 100644
--- a/include/common/http-hdr.h
+++ b/include/common/http-hdr.h
@@ -28,7 +28,7 @@
 #define _COMMON_HTTP_HDR_H
 
 #include <inttypes.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 /* a header field made of a name and a value. Such structure stores 4 longs so
  * it takes 16 bytes on 32-bit systems and 32 bytes on 64-bit systems.
diff --git a/include/common/http.h b/include/common/http.h
index acf19903f..86cf01536 100644
--- a/include/common/http.h
+++ b/include/common/http.h
@@ -24,7 +24,7 @@
 #define _COMMON_HTTP_H
 
 #include <common/buf.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 /*
  * some macros mainly used when parsing header fields.
diff --git a/include/common/htx.h b/include/common/htx.h
index 5a13614f3..1a87cde75 100644
--- a/include/common/htx.h
+++ b/include/common/htx.h
@@ -25,7 +25,7 @@
 #include <stdio.h>
 #include <haproxy/api.h>
 #include <common/buf.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/http.h>
 #include <common/http-hdr.h>
 #include <common/standard.h>
diff --git a/include/common/istbuf.h b/include/common/istbuf.h
index a533c7174..f9bf0b1f9 100644
--- a/include/common/istbuf.h
+++ b/include/common/istbuf.h
@@ -30,7 +30,7 @@
 
 #include <inttypes.h>
 #include <common/buf.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 
 /* b_isteq() : returns > 0 if the first <n> characters of buffer <b> starting
diff --git a/include/common/ist.h b/include/import/ist.h
similarity index 99%
rename from include/common/ist.h
rename to include/import/ist.h
index d62924e16..08e211938 100644
--- a/include/common/ist.h
+++ b/include/import/ist.h
@@ -1,8 +1,8 @@
 /*
- * include/common/ist.h
+ * include/import/ist.h
  * Very simple indirect string manipulation functions.
  *
- * Copyright (C) 2014-2017 Willy Tarreau - w@1wt.eu
+ * Copyright (C) 2014-2020 Willy Tarreau - w@1wt.eu
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -25,19 +25,18 @@
  * OTHER DEALINGS IN THE SOFTWARE.
  */
 
-#ifndef _COMMON_IST_H
-#define _COMMON_IST_H
+#ifndef _IMPORT_IST_H
+#define _IMPORT_IST_H
 
+#include <sys/types.h>
 #include <ctype.h>
+#include <stddef.h>
 #include <string.h>
-#include <unistd.h>
 
 #ifndef IST_FREESTANDING
 #include <stdlib.h>
 #endif
 
-#include <haproxy/api.h>
-
 /* ASCII to lower case conversion table */
 #define _IST_LC ((const unsigned char[256]){            \
 	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
@@ -658,7 +657,7 @@ static inline const char *ist_find_ctl(const struct ist ist)
 	last += sizeof(long);
 	if (__builtin_expect(curr < last, 0)) {
 		do {
-			if ((uint8_t)*curr < 0x20)
+			if ((unsigned char)*curr < 0x20)
 				return curr;
 			curr++;
 		} while (curr < last);
@@ -794,7 +793,7 @@ static inline struct ist istdup(const struct ist src)
 	/* Allocate at least 1 byte to allow duplicating an empty string with
 	 * malloc implementations that return NULL for a 0-size allocation.
 	 */
-	struct ist dst = istalloc(MAX(src_size, 1));
+	struct ist dst = istalloc(src_size ? src_size : 1);
 
 	if (isttest(dst)) {
 		istcpy(&dst, src, src_size);
diff --git a/include/proto/connection.h b/include/proto/connection.h
index 9b1e3d871..2efd629fc 100644
--- a/include/proto/connection.h
+++ b/include/proto/connection.h
@@ -23,7 +23,7 @@
 #define _PROTO_CONNECTION_H
 
 #include <haproxy/api.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/memory.h>
 #include <types/connection.h>
 #include <types/listener.h>
diff --git a/include/proto/h1_htx.h b/include/proto/h1_htx.h
index a8fd88675..13ba394d5 100644
--- a/include/proto/h1_htx.h
+++ b/include/proto/h1_htx.h
@@ -24,7 +24,7 @@
 #define _PROTO_H1_HTX_H
 
 #include <common/buf.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/h1.h>
 
 int h1_parse_msg_hdrs(struct h1m *h1m, union h1_sl *h1sl, struct htx *dsthtx,
diff --git a/include/proto/http_htx.h b/include/proto/http_htx.h
index 557d34f45..edbd8f1bf 100644
--- a/include/proto/http_htx.h
+++ b/include/proto/http_htx.h
@@ -24,7 +24,7 @@
 #define _PROTO_HTTP_HTX_H
 
 #include <common/buf.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/regex.h>
 
 #include <types/http_htx.h>
diff --git a/include/proto/ring.h b/include/proto/ring.h
index 8adbb9c52..6f393fe43 100644
--- a/include/proto/ring.h
+++ b/include/proto/ring.h
@@ -23,7 +23,7 @@
 #define _PROTO_RING_H
 
 #include <stdlib.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <types/ring.h>
 
 struct ring *ring_new(size_t size);
diff --git a/include/proto/trace.h b/include/proto/trace.h
index ef88079b1..f43faf5a9 100644
--- a/include/proto/trace.h
+++ b/include/proto/trace.h
@@ -24,7 +24,7 @@
 
 #include <haproxy/api.h>
 #include <common/buffer.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/mini-clist.h>
 #include <types/log.h>
 #include <types/sink.h>
diff --git a/include/types/checks.h b/include/types/checks.h
index b2be640c3..4b8177078 100644
--- a/include/types/checks.h
+++ b/include/types/checks.h
@@ -17,7 +17,7 @@
 #include <import/ebpttree.h>
 
 #include <common/standard.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/mini-clist.h>
 #include <common/regex.h>
 #include <common/buf.h>
diff --git a/include/types/connection.h b/include/types/connection.h
index 7357174dc..601e5056c 100644
--- a/include/types/connection.h
+++ b/include/types/connection.h
@@ -26,7 +26,7 @@
 #include <sys/socket.h>
 
 #include <haproxy/api-t.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 #include <types/listener.h>
 #include <types/obj_type.h>
diff --git a/include/types/fcgi-app.h b/include/types/fcgi-app.h
index f0fcdc7ae..7fb20ee6f 100644
--- a/include/types/fcgi-app.h
+++ b/include/types/fcgi-app.h
@@ -23,7 +23,7 @@
 #define _TYPES_HTTP_FCGI_H
 
 #include <haproxy/api-t.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/fcgi.h>
 #include <common/mini-clist.h>
 #include <common/regex.h>
diff --git a/include/types/fd.h b/include/types/fd.h
index 0041d4d60..7ec97bc74 100644
--- a/include/types/fd.h
+++ b/include/types/fd.h
@@ -24,7 +24,7 @@
 
 #include <haproxy/api-t.h>
 #include <common/hathreads.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <types/port_range.h>
 
 /* Direction for each FD event update */
diff --git a/include/types/http_htx.h b/include/types/http_htx.h
index 301034c8f..02b6b3b48 100644
--- a/include/types/http_htx.h
+++ b/include/types/http_htx.h
@@ -28,7 +28,7 @@
 #include <common/buf.h>
 #include <common/http.h>
 #include <common/htx.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 /* Context used to find/remove an HTTP header. */
 struct http_hdr_ctx {
diff --git a/include/types/ring.h b/include/types/ring.h
index ac93c1219..f3b3987a8 100644
--- a/include/types/ring.h
+++ b/include/types/ring.h
@@ -24,7 +24,7 @@
 
 #include <haproxy/api-t.h>
 #include <common/buf.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 /* The code below handles circular buffers with single-producer and multiple
  * readers (up to 255). The buffer storage area must remain always allocated.
diff --git a/include/types/sink.h b/include/types/sink.h
index 64b0bcaf4..b10cb8912 100644
--- a/include/types/sink.h
+++ b/include/types/sink.h
@@ -24,7 +24,7 @@
 
 #include <haproxy/api-t.h>
 #include <common/buffer.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 /* A sink may be of 4 distinct types :
  *   - file descriptor (such as stdout)
diff --git a/include/types/trace.h b/include/types/trace.h
index cd5e8be15..ad9d7b6a0 100644
--- a/include/types/trace.h
+++ b/include/types/trace.h
@@ -24,7 +24,7 @@
 
 #include <haproxy/api-t.h>
 #include <common/buffer.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/mini-clist.h>
 #include <types/sink.h>
 
diff --git a/src/debug.c b/src/debug.c
index 7f281f029..e1b9070bf 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -23,7 +23,7 @@
 #include <common/buf.h>
 #include <common/debug.h>
 #include <common/hathreads.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/net_helper.h>
 #include <common/standard.h>
 
diff --git a/src/h2.c b/src/h2.c
index 891c3e06c..c94ea8e03 100644
--- a/src/h2.c
+++ b/src/h2.c
@@ -29,7 +29,7 @@
 #include <haproxy/api.h>
 #include <common/h2.h>
 #include <common/http-hdr.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <types/global.h>
 
 struct h2_frame_definition h2_frame_definition[H2_FT_ENTRIES] =	{
diff --git a/src/hpack-dec.c b/src/hpack-dec.c
index fa25ac475..50293d850 100644
--- a/src/hpack-dec.c
+++ b/src/hpack-dec.c
@@ -36,7 +36,7 @@
 #include <common/hpack-tbl.h>
 #include <common/chunk.h>
 #include <common/h2.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 #include <types/global.h>
 
diff --git a/src/hpack-enc.c b/src/hpack-enc.c
index 1a6fa1cc8..bf7336b08 100644
--- a/src/hpack-enc.c
+++ b/src/hpack-enc.c
@@ -32,7 +32,7 @@
 
 #include <common/hpack-enc.h>
 #include <common/http-hdr.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 #include <types/global.h>
 
diff --git a/src/hpack-tbl.c b/src/hpack-tbl.c
index effe5e01e..31c24b21f 100644
--- a/src/hpack-tbl.c
+++ b/src/hpack-tbl.c
@@ -32,7 +32,7 @@
 
 #include <common/hpack-huff.h>
 #include <common/hpack-tbl.h>
-#include <common/ist.h>
+#include <import/ist.h>
 
 #include <types/global.h>
 
diff --git a/src/mux_fcgi.c b/src/mux_fcgi.c
index 5ce6f6191..7ff39328c 100644
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -15,7 +15,7 @@
 #include <common/fcgi.h>
 #include <common/h1.h>
 #include <common/htx.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/mini-clist.h>
 #include <common/net_helper.h>
 
diff --git a/src/sink.c b/src/sink.c
index 20d3d79b1..7eb283fc6 100644
--- a/src/sink.c
+++ b/src/sink.c
@@ -20,7 +20,7 @@
 
 #include <haproxy/api.h>
 #include <common/cfgparse.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/mini-clist.h>
 #include <common/time.h>
 #include <proto/cli.h>
diff --git a/src/trace.c b/src/trace.c
index 667cd81ca..3f6ff0543 100644
--- a/src/trace.c
+++ b/src/trace.c
@@ -20,7 +20,7 @@
 
 #include <haproxy/api.h>
 #include <common/buffer.h>
-#include <common/ist.h>
+#include <import/ist.h>
 #include <common/mini-clist.h>
 #include <proto/cli.h>
 #include <proto/log.h>