diff --git a/cia.c b/cia.c
index adbd990..b640837 100644
--- a/cia.c
+++ b/cia.c
@@ -30,6 +30,7 @@
 #include "src/stdlib-thread/thread.c"
 
 // Module stdlib_file
+#include "src/stdlib-file/common.c"
 #include "src/stdlib-file/file.c"
 #include "src/stdlib-file/fmt.c"
 
diff --git a/src/stdlib-file/common.c b/src/stdlib-file/common.c
new file mode 100644
index 0000000..e6dfd39
--- /dev/null
+++ b/src/stdlib-file/common.c
@@ -0,0 +1,8 @@
+
+FILE *stdin;
+FILE *stdout;
+FILE *stderr;
+
+static Cia_Pool _page_allocator;
+static Cia_Pool _file_pool;
+static Cia_Mutex _g_pool_mutex;
diff --git a/src/stdlib-file/file.c b/src/stdlib-file/file.c
index 533aa30..1c68464 100644
--- a/src/stdlib-file/file.c
+++ b/src/stdlib-file/file.c
@@ -1,12 +1,4 @@
 
-FILE *stdin;
-FILE *stdout;
-FILE *stderr;
-
-static Cia_Pool _page_allocator;
-static Cia_Pool _file_pool;
-static Cia_Mutex _g_pool_mutex;
-
 static void _fileapi_init() {
     cia_pool_create(&_file_pool, cia_allocator_pages(), 0x1000, sizeof(FILE), 16);
     stdin = cia_pool_alloc(&_file_pool);
diff --git a/src/stdlib-file/fmt.c b/src/stdlib-file/fmt.c
index 28cb017..276cf61 100644
--- a/src/stdlib-file/fmt.c
+++ b/src/stdlib-file/fmt.c
@@ -82,6 +82,7 @@ int printf(const char *restrict fmt, ...) {
     i64 buf_start_idx = 0;
     i64 buf_end_idx = 0;
     u64 unused;
+    cia_mutex_lock(&stdout->mutex);
     for(i64 i = 0; fmt[i] != 0;) {
         buf_start_idx = i;
         buf_end_idx = i;
@@ -98,7 +99,7 @@ int printf(const char *restrict fmt, ...) {
                 , &unused
             );
             if(status != _RT_STATUS_OK) {
-                return -1;
+                goto _error;
             }
             ret_printed += buf_size;
         }
@@ -129,16 +130,21 @@ int printf(const char *restrict fmt, ...) {
             int ch = va_arg(args, int);
             _RT_Status status = _rt_file_write(&stdout->rt_file, 1, &ch, &unused);
             if(status != _RT_STATUS_OK) {
-                return -1;
+                goto _error;
             }
             arg_chars = 1;
         }
         i += 1;
         if(arg_chars < 0) {
-            return -1;
+            goto _error;
         }
         ret_printed += arg_chars;
     }
+    cia_mutex_unlock(&stdout->mutex);
     va_end(args);
     return ret_printed;
+_error:
+    cia_mutex_unlock(&stdout->mutex);
+    va_end(args);
+    return -1;
 }