diff --git a/src/mux_h1.c b/src/mux_h1.c
index 1c75e93..963ed16 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -10,6 +10,7 @@
  *
  */
 #include <haproxy/api.h>
+#include <haproxy/istbuf.h>
 #include <common/cfgparse.h>
 #include <common/h1.h>
 #include <common/h2.h>