diff --git a/examples/python/CMakeLists.txt b/examples/python/CMakeLists.txt
index 6717165418..5f88462606 100644
--- a/examples/python/CMakeLists.txt
+++ b/examples/python/CMakeLists.txt
@@ -4,6 +4,7 @@ endif()
 
 file(GLOB PYTHON_SRCS "*.py")
 # Remove too long examples
+list(FILTER PYTHON_SRCS EXCLUDE REGEX ".*/line_balancing_sat.py") # need input file
 list(FILTER PYTHON_SRCS EXCLUDE REGEX ".*/arc_flow_cutting_stock_sat.py") # too long
 list(FILTER PYTHON_SRCS EXCLUDE REGEX ".*/bus_driver_scheduling_sat.py") # too long
 list(FILTER PYTHON_SRCS EXCLUDE REGEX ".*/cover_rectangle_sat.py") # too long
diff --git a/examples/python/line_balancing_sat.py b/examples/python/line_balancing_sat.py
old mode 100644
new mode 100755
index 9bf8e629b8..96079397d7
--- a/examples/python/line_balancing_sat.py
+++ b/examples/python/line_balancing_sat.py
@@ -340,6 +340,8 @@ def solve_scheduling_model(model, hint):
 def main(argv: Sequence[str]) -> None:
     if len(argv) > 1:
         raise app.UsageError('Too many command-line arguments.')
+    if FLAGS.input == '':
+        raise app.UsageError('Missing input file.')
 
     model = read_model(FLAGS.input)
     print_stats(model)