diff --git a/core/gcc/build b/core/gcc/build
index ad78f443..096a5a8d 100755
--- a/core/gcc/build
+++ b/core/gcc/build
@@ -41,3 +41,6 @@ rm -rf "$1/usr/share/info"
 
 # Some legacy programs will expect cc
 ln -s gcc "$1/usr/bin/cc"
+
+# POSIX compliance.
+install -Dm755 ../c99 "$1/usr/bin/c99"
diff --git a/core/gcc/checksums b/core/gcc/checksums
index 9485200c..cd53b1c4 100644
--- a/core/gcc/checksums
+++ b/core/gcc/checksums
@@ -1 +1,2 @@
 64baadfe6cc0f4947a84cb12d7f0dfaf45bb58b7e92461639596c21e02d97d2c  gcc-8.3.0.tar.xz
+765614b3396d70bca3fa0ae4a813632486c6dca320e2bd13c8c39dca52be4a4c  c99
diff --git a/core/gcc/files/c99 b/core/gcc/files/c99
new file mode 100644
index 00000000..692f0924
--- /dev/null
+++ b/core/gcc/files/c99
@@ -0,0 +1,2 @@
+#!/bin/sh
+exec cc -std=c99 "$@"
diff --git a/core/gcc/sources b/core/gcc/sources
index 6c0c8c38..755fc46e 100644
--- a/core/gcc/sources
+++ b/core/gcc/sources
@@ -1 +1,2 @@
 https://gcc.gnu.org/pub/gcc/releases/gcc-8.3.0/gcc-8.3.0.tar.xz gcc
+files/c99