--- a/platform/linux-alpine.c
+++ b/platform/linux-alpine.c
@@ -14,16 +14,13 @@ void platform_init(void) {
 }
 
 void platform_stdinc_paths(StringArray *paths) {
-  // Replace this block with absolute path if you intend to
-  // execute the compiler outside of source directory.
+  // Allow running tests from source directory before installation.
   {
     char *src_dir = source_dir();
-    if (!file_exists(format("%s/include/.slimcc_incl_dir", src_dir)))
-      error("can't find built-in headers");
-
     add_include_path(paths, format("%s/include", src_dir));
   }
 
+  add_include_path(paths, "/usr/lib/slimcc/include");
   add_include_path(paths, "/usr/include");
 }