diff --git a/km3buu/output.py b/km3buu/output.py
index c15df73d4a5705cee062951d16baa840e436d97a..123a5bbe87c5aa286f57f61853ede21aff5f7fe9 100644
--- a/km3buu/output.py
+++ b/km3buu/output.py
@@ -33,7 +33,7 @@ try:
     libpath = environ.get("KM3NET_LIB")
     if libpath is None:
         libpath = Config().km3net_lib_path
-    if ROOT.gSystem.Load(join(libpath, "libKM3NeTROOT.so")) != 0:
+    if ROOT.gSystem.Load(join(libpath, "libKM3NeTROOT.so")) < 0:
         raise ModuleNotFoundError("KM3NeT dataformat library not found!")
 except ModuleNotFoundError:
     import warnings
diff --git a/km3buu/tests/test_output.py b/km3buu/tests/test_output.py
index 0387b2482d61d5b486f053fdb7e35eb10fad4e61..b383db705e7a6f35761a2120075ac7478c9c86f1 100644
--- a/km3buu/tests/test_output.py
+++ b/km3buu/tests/test_output.py
@@ -31,7 +31,7 @@ try:
     if libpath is None:
         libpath = Config().km3net_lib_path
     KM3NET_LIB_AVAILABLE = (ROOT.gSystem.Load(join(libpath,
-                                                   "libKM3NeTROOT.so")) == 0)
+                                                   "libKM3NeTROOT.so")) >= 0)
 except ModuleNotFoundError:
     KM3NET_LIB_AVAILABLE = False