diff --git a/src/shell/CMakeLists.txt b/src/shell/CMakeLists.txt
index 074c17886..03ee0b69d 100644
--- a/src/shell/CMakeLists.txt
+++ b/src/shell/CMakeLists.txt
@@ -18,6 +18,8 @@ add_test(lean_luahook2 ${CMAKE_CURRENT_BINARY_DIR}/lean -c 100 "${LEAN_SOURCE_DI
 add_test(lean_lua1 ${LEAN_SOURCE_DIR}/cmake/redirect.sh "${CMAKE_CURRENT_BINARY_DIR}/lean" "--lua" "${LEAN_SOURCE_DIR}/../tests/lua/single.lua")
 add_test(lean_lua2 ${LEAN_SOURCE_DIR}/cmake/redirect.sh "${CMAKE_CURRENT_BINARY_DIR}/lean" "-u" "${LEAN_SOURCE_DIR}/../tests/lua/single.lua")
 add_test(lean_unknown_option ${LEAN_SOURCE_DIR}/cmake/check_failure.sh "${CMAKE_CURRENT_BINARY_DIR}/lean" "-z")
+add_test(lean_unknown_file1 ${LEAN_SOURCE_DIR}/cmake/check_failure.sh "${CMAKE_CURRENT_BINARY_DIR}/lean" "boofoo.lean")
+add_test(lean_unknown_file2 ${LEAN_SOURCE_DIR}/cmake/check_failure.sh "${CMAKE_CURRENT_BINARY_DIR}/lean" "boofoo.lua")
 
 
 # LEAN EXAMPLES
diff --git a/src/shell/lean.cpp b/src/shell/lean.cpp
index 41cad92c2..09854d938 100644
--- a/src/shell/lean.cpp
+++ b/src/shell/lean.cpp
@@ -158,6 +158,10 @@ int main(int argc, char ** argv) {
             }
             if (k == input_kind::Lean) {
                 std::ifstream in(argv[i]);
+                if (in.bad() || in.fail()) {
+                    std::cerr << "Failed to open file '" << argv[i] << "'\n";
+                    return 1;
+                }
                 parser p(f, in, &S, false, false);
                 if (!p())
                     ok = false;