diff --git a/gcc-test/build.rs b/gcc-test/build.rs
index 696ea12..95291bc 100644
--- a/gcc-test/build.rs
+++ b/gcc-test/build.rs
@@ -3,11 +3,14 @@ extern crate gcc;
 fn main() {
     gcc::Config::new()
                 .file("src/foo.c")
+                .define("FOO", None)
+                .define("BAR", Some("1"))
                 .compile("libfoo.a");
 
     gcc::Config::new()
                 .file("src/bar1.c")
                 .file("src/bar2.c")
+                .include("src/include")
                 .compile("libbar.a");
 
     gcc::Config::new()
diff --git a/gcc-test/src/bar1.c b/gcc-test/src/bar1.c
index b2e30f9..605be33 100644
--- a/gcc-test/src/bar1.c
+++ b/gcc-test/src/bar1.c
@@ -1,4 +1,5 @@
 #include <stdint.h>
+#include "foo.h"
 
 int32_t bar1() {
   return 5;
diff --git a/gcc-test/src/foo.c b/gcc-test/src/foo.c
index ee16f6f..541e62c 100644
--- a/gcc-test/src/foo.c
+++ b/gcc-test/src/foo.c
@@ -1,5 +1,9 @@
 #include <stdint.h>
 
+#ifdef FOO
+#if BAR == 1
 int32_t foo() {
   return 4;
 }
+#endif
+#endif
diff --git a/gcc-test/src/include/foo.h b/gcc-test/src/include/foo.h
new file mode 100644
index 0000000..e69de29