diff --git a/doc/mk_api_doc.py b/doc/mk_api_doc.py
index 3a2343803..a944f2c65 100644
--- a/doc/mk_api_doc.py
+++ b/doc/mk_api_doc.py
@@ -288,7 +288,14 @@ try:
         # Put z3py at the beginning of the search path to try to avoid picking up
         # an installed copy of Z3py.
         sys.path.insert(0, os.path.dirname(Z3PY_PACKAGE_PATH))
-        sys.path.insert(0, os.path.dirname(BUILD_DIR))
+
+        if sys.version < '3':
+            import __builtin__
+            __builtin__.Z3_LIB_DIRS = [ BUILD_DIR ]
+        else:
+            import builtins
+            builtins.Z3_LIB_DIRS = [ BUILD_DIR ]
+
         for modulename in (
                 'z3',
                 'z3.z3consts',