diff --git a/lang/CMakeLists.txt b/lang/CMakeLists.txt
index ad0c1b0..55e9c86 100644
--- a/lang/CMakeLists.txt
+++ b/lang/CMakeLists.txt
@@ -7,5 +7,5 @@
 project(TardisLang)
 file(GLOB SRC_FILES "${PROJECT_SOURCE_DIR}/*.c")
 add_executable(TardisLang ${SRC_FILES})
-set_property(TARGET TardisLang PROPERTY C_STANDARD 99)
+set_property(TARGET TardisLang PROPERTY C_STANDARD 11)
 target_compile_options(TardisLang PRIVATE -Wall -Wextra -Wpedantic -Werror -fwrapv -fno-strict-aliasing -fsigned-char)
diff --git a/lang/main.c b/lang/main.c
index c63171d..1fd46c9 100644
--- a/lang/main.c
+++ b/lang/main.c
@@ -4,6 +4,8 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <threads.h>
+#include <stdatomic.h>
 
 #define SYMBOL_LEN 32
 #define SYMBOLS_MAX 32
@@ -13,29 +15,33 @@
 } symbol;
 
 symbol symbols[SYMBOLS_MAX] = {0};
+mtx_t symbols_lock;
 
 int find_symbol(char *name) {
-	// TODO: thread safety
+	mtx_lock(&symbols_lock);
 	for(int i = 0; i < SYMBOLS_MAX; ++i) {
 		symbol *curr_sym = &symbols[i];
 		char *curr_name = curr_sym->name;
 		if(curr_name[0] == 0) {
 			strncpy(curr_name, name, SYMBOL_LEN);
+			mtx_unlock(&symbols_lock);
 			return i;
 		} else {
 			int cmp = strncmp(curr_name, name, SYMBOL_LEN);
 			if(cmp == 0) {
+				mtx_unlock(&symbols_lock);
 				return i;
 			}
 		}
 	}
+	mtx_unlock(&symbols_lock);
 	printf("ERROR: ran out of symbols\n");
 	abort();
 }
 
 typedef struct {
 	int value;
-	int refcount;
+	atomic_int refcount;
 } object;
 
 object *create_object(int value) {
@@ -50,11 +56,10 @@
 }
 
 void drop_object(object **objptr) {
-	// TODO: thread safety
 	if(*objptr) {
 		object *obj = *objptr;
-		obj->refcount--;
-		if(obj->refcount == 0) {
+		atomic_int count = atomic_fetch_sub_explicit(&obj->refcount, 1, memory_order_relaxed);
+		if(count == 1) {
 			printf("freeing %p\n", (void*)obj);
 			free(obj);
 		}
@@ -84,6 +89,7 @@
 }
 
 int main(void) {
+	mtx_init(&symbols_lock, mtx_plain);
 	printf("Hello world!\n");
 	printf("symb %i\n", find_symbol("a"));
 	printf("symb %i\n", find_symbol("b"));