diff --git a/media-gfx/iscan/files/iscan-2.30.4.2-c99.patch b/media-gfx/iscan/files/iscan-2.30.4.2-c99.patch
new file mode 100644
index 0000000000000..93683c2887b4f
--- /dev/null
+++ b/media-gfx/iscan/files/iscan-2.30.4.2-c99.patch
@@ -0,0 +1,24 @@
+--- a/backend/defines.h	2021-01-04 08:13:48.995137756 -0000
++++ b/backend/defines.h	2021-01-04 08:16:00.524563361 -0000
+@@ -31,6 +31,13 @@
+ 
+ 
+ #ifndef __cplusplus
++
++/*  Use the C99 bool type if available
++ */
++#ifdef HAVE_STDBOOL_H
++#include <stdbool.h>
++#else
++
+ /*! A C++ Boolean type and corresponding keywords for our C code.
+  */
+ typedef enum {
+@@ -38,6 +45,7 @@
+   true
+ } bool;
+ #endif
++#endif
+ 
+ 
+ /*  Run-time contract validation.
diff --git a/media-gfx/iscan/iscan-2.30.4.2-r1.ebuild b/media-gfx/iscan/iscan-2.30.4.2-r1.ebuild
index 333d41b9b1c7f..c1eb390986e3b 100644
--- a/media-gfx/iscan/iscan-2.30.4.2-r1.ebuild
+++ b/media-gfx/iscan/iscan-2.30.4.2-r1.ebuild
@@ -1,4 +1,4 @@
-# Copyright 1999-2020 Gentoo Authors
+# Copyright 1999-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=7
@@ -70,6 +70,7 @@ PATCHES=(
 	"${FILESDIR}"/iscan-2.30.1.1-gcc6.patch
 	"${FILESDIR}"/iscan-2.30.3.1-fix-x86-unknown-types.patch
 	"${FILESDIR}"/iscan-2.30.4.2-sscanf.patch
+	"${FILESDIR}"/iscan-2.30.4.2-c99.patch
 )
 
 QA_PRESTRIPPED="usr/lib.*/libesmod.so.*"