diff --git a/src/iri2016/base.py b/src/iri2016/base.py
index 1ae76be..06d0fa8 100644
--- a/src/iri2016/base.py
+++ b/src/iri2016/base.py
@@ -26,8 +26,8 @@ def IRI(time: str | datetime, altkmrange: list[float], glat: float, glon: float)
     iri_name = "iri2016_driver"
     if os.name == "nt":
         iri_name += ".exe"
-
-    build()
+    if not importlib.resources.is_resource(__package__, iri_name):
+        build()
     # %% run IRI
     with importlib.resources.path(__package__, iri_name) as exe:
         cmd = [
diff --git a/src/iri2016/src/iri2016_driver.f90 b/src/iri2016/src/iri2016_driver.f90
index 71cc577..d40aed1 100644
--- a/src/iri2016/src/iri2016_driver.f90
+++ b/src/iri2016/src/iri2016_driver.f90
@@ -23,6 +23,7 @@
 jf(26) = .true.  ! jf(26) == jf(8) == .true. for foF2
 jf(28:30) = .false.
 jf(33:35) = .false.
+jf(39)    = .false. !hmF2-old -> AMTB-model
 
 ! --- command line input
 if (command_argument_count() < 12) then