diff --git a/doc/04-schema.md b/doc/04-schema.md
index 0bb286f3e..3c179eb63 100644
--- a/doc/04-schema.md
+++ b/doc/04-schema.md
@@ -225,6 +225,16 @@ Example:
         }
     }
 
+### include-paths
+
+A list of paths which should get appended to PHP's `include_path`.
+
+Example:
+
+    {
+        "include-paths": ["lib/"]
+    }
+
 ### target-dir
 
 Defines the installation target.