diff --git a/libc/src/stdio.cpp b/libc/src/stdio.cpp
index d58cae21..0ce0b5fc 100644
--- a/libc/src/stdio.cpp
+++ b/libc/src/stdio.cpp
@@ -11,6 +11,13 @@ FILE* stdin = nullptr;
 FILE* stderr = nullptr;
 FILE* stdout = nullptr;
 
+static const char* read_tmpdir()
+{
+    const char* tmpdir = getenv("TMPDIR");
+    if (!tmpdir) return "/tmp";
+    return tmpdir;
+}
+
 static int fopen_parse_mode(const char* mode)
 {
     int result = 0;
@@ -477,8 +484,7 @@ extern "C"
 
     FILE* tmpfile()
     {
-        // FIXME: use /tmp as the directory when the tmpfs is mounted only there.
-        int fd = open("/", O_RDWR | O_TMPFILE, 0600);
+        int fd = open(read_tmpdir(), O_RDWR | O_TMPFILE, 0600);
         if (fd < 0) return nullptr;
 
         FILE* f = fdopen(fd, "w+b");