diff --git a/src/frontends/lean/server.cpp b/src/frontends/lean/server.cpp
index 65cb0cca1..f148c0e01 100644
--- a/src/frontends/lean/server.cpp
+++ b/src/frontends/lean/server.cpp
@@ -238,6 +238,9 @@ server::server(environment const & env, io_state const & ios, unsigned num_threa
     m_env(env), m_ios(ios), m_out(ios.get_regular_channel().get_stream()),
     m_num_threads(num_threads), m_empty_snapshot(m_env, m_ios.get_options()),
     m_worker(env, ios, m_cache) {
+#if !defined(LEAN_MULTI_THREAD)
+    lean_unreachable();
+#endif
 }
 
 server::~server() {
diff --git a/src/shell/CMakeLists.txt b/src/shell/CMakeLists.txt
index 84fc68b72..4718d0a07 100644
--- a/src/shell/CMakeLists.txt
+++ b/src/shell/CMakeLists.txt
@@ -47,6 +47,7 @@ FOREACH(T ${LEANRUNTESTS})
            COMMAND "./test_single.sh" "${CMAKE_CURRENT_BINARY_DIR}/lean" ${T_NAME})
 ENDFOREACH(T)
 
+if("${MULTI_THREAD}" MATCHES "ON")
 # LEAN INTERACTIVE TESTS
 file(GLOB LEANITTESTS "${LEAN_SOURCE_DIR}/../tests/lean/interactive/*.input")
 FOREACH(T ${LEANITTESTS})
@@ -55,6 +56,7 @@ FOREACH(T ${LEANITTESTS})
            WORKING_DIRECTORY "${LEAN_SOURCE_DIR}/../tests/lean/interactive"
            COMMAND "./test_single.sh" "${CMAKE_CURRENT_BINARY_DIR}/lean" ${T_NAME})
 ENDFOREACH(T)
+endif()
 
 # LEAN SLOW TESTS
 file(GLOB LEANSLOWTESTS "${LEAN_SOURCE_DIR}/../tests/lean/slow/*.lean")
diff --git a/src/shell/lean.cpp b/src/shell/lean.cpp
index f901214e7..a082bc636 100644
--- a/src/shell/lean.cpp
+++ b/src/shell/lean.cpp
@@ -78,8 +78,10 @@ static void display_help(std::ostream & out) {
     std::cout << "                    0 means 'do not check'.\n";
     std::cout << "  --trust=num -t    trust level (default: 0) \n";
     std::cout << "  --quiet -q        do not print verbose messages\n";
+#if defined(LEAN_MULTI_THREAD)
     std::cout << "  --server          start Lean in 'server' mode\n";
     std::cout << "  --threads=num -j  number of threads used to process lean files\n";
+#endif
     std::cout << "  --deps            just print dependencies of a Lean input\n";
     std::cout << "  --flycheck        print structured error message for flycheck\n";
     std::cout << "  --cache=file -c   load/save cached definitions from/to the given file\n";
@@ -113,9 +115,11 @@ static struct option g_long_options[] = {
     {"githash",     no_argument,       0, 'g'},
     {"output",      required_argument, 0, 'o'},
     {"trust",       required_argument, 0, 't'},
+#if defined(LEAN_MULTI_THREAD)
     {"server",      no_argument,       0, 'S'},
-    {"quiet",       no_argument,       0, 'q'},
     {"threads",     required_argument, 0, 'j'},
+#endif
+    {"quiet",       no_argument,       0, 'q'},
     {"cache",       required_argument, 0, 'c'},
     {"deps",        no_argument,       0, 'D'},
     {"flycheck",    no_argument,       0, 'F'},
@@ -126,10 +130,14 @@ static struct option g_long_options[] = {
     {0, 0, 0, 0}
 };
 
-#if defined(LEAN_USE_BOOST)
-static char const * g_opt_str = "FDSqlupgvhj:012k:012s:012t:012o:c:i:";
+#define BASIC_OPT_STR "FDqlupgvhk:012t:012o:c:i:"
+
+#if defined(LEAN_USE_BOOST) && defined(LEAN_MULTI_THREAD)
+static char const * g_opt_str = BASIC_OPT_STR "Sj:012s:012";
+#elif !defined(LEAN_USE_BOOST) && defined(LEAN_MULTI_THREAD)
+static char const * g_opt_str = BASIC_OPT_STR "Sj:012";
 #else
-static char const * g_opt_str = "FDSqlupgvhj:012k:012t:012o:c:i:";
+static char const * g_opt_str = BASIC_OPT_STR;
 #endif
 
 class simple_pos_info_provider : public pos_info_provider {
@@ -223,6 +231,11 @@ int main(int argc, char ** argv) {
         }
     }
 
+    #if !defined(LEAN_MULTI_THREAD)
+    lean_assert(!server);
+    lean_assert(num_threads == 1);
+    #endif
+
     environment env = mk_environment(trust_lvl);
     io_state ios(lean::mk_pretty_formatter_factory());
     if (quiet)