diff --git a/endless-sky-0.9.8-environment.patch b/endless-sky-0.9.8-environment.patch
new file mode 100644
index 0000000..ace85b4
--- /dev/null
+++ b/endless-sky-0.9.8-environment.patch
@@ -0,0 +1,12 @@
+diff -up SConstruct.path SConstruct
+--- SConstruct.path	2019-01-15 16:29:57.084998841 +0000
++++ SConstruct	2019-01-15 16:33:21.014998063 +0000
+@@ -1,7 +1,7 @@
+ import os
+ 
+ # Load any environment variables that alter the build.
+-env = Environment()
++env = Environment(ENV = os.environ)
+ if 'CCFLAGS' in os.environ:
+ 	env.Append(CCFLAGS = os.environ['CCFLAGS'])
+ if 'CXXFLAGS' in os.environ:
diff --git a/endless-sky.spec b/endless-sky.spec
index f25beed..b42b29f 100644
--- a/endless-sky.spec
+++ b/endless-sky.spec
@@ -2,7 +2,7 @@
 
 Name:		endless-sky
 Version:	0.9.8
-Release:	8%{?dist}
+Release:	9%{?dist}
 Summary:	Space exploration, trading, and combat game
 
 License:	GPLv3
@@ -15,6 +15,10 @@ Source0:	https://github.com/%{name}/%{name}/archive/%{gittag0}.tar.gz#/%{name}-%
 Patch0:		endless-sky-0.8.10-remove-games-path.patch
 # Unset CCFLAGS override inside SConstruct.
 Patch1:		endless-sky-0.9.4-remove-additional-ccflags.patch
+# Pass the entire environment to build commands; RPM already standardizes the
+# environment. This is needed for CPLUS_INCLUDE_PATH for the Flatpak build,
+# but potentially for other things as well.
+Patch2:		endless-sky-0.9.8-environment.patch
 
 Requires:	%{name}-data = %{version}-%{release}
 BuildRequires:	scons
@@ -100,6 +104,10 @@ install -m644 -D endless-sky.appdata.xml %{buildroot}%{_datadir}/appdata/%{name}
 
 
 %changelog
+* Tue Jan 15 2019 fedora-toolbox <otaylor@redhat.com> - 0.9.8-9
+- Pass the entire environment to build commands; fixes CPLUS_INCLUDE_PATH for
+  flatpaks.
+
 * Fri Sep  7 2018 Owen Taylor <otaylor@redhat.com> - 0.9.8-8
 - scons is in /usr/bin, even if we're compiling with a different %%{_prefix}