diff --git a/kernel/src/sys/exec.cpp b/kernel/src/sys/exec.cpp
index a65a503b..53c615ce 100644
--- a/kernel/src/sys/exec.cpp
+++ b/kernel/src/sys/exec.cpp
@@ -6,6 +6,7 @@
 #include "thread/Scheduler.h"
 #include "thread/ThreadImage.h"
 #include <bits/modes.h>
+#include <bits/open-flags.h>
 #include <luna/CString.h>
 #include <luna/ScopeGuard.h>
 #include <luna/Vector.h>
@@ -76,8 +77,11 @@ Result<u64> sys_exec(Registers* regs, SyscallArgs args)
 
     guard.deactivate();
 
-    // FIXME: Close O_CLOEXEC file descriptors.
-    // for (int i = 0; i < FD_MAX; i++) { current->fd_table[i] = {}; }
+    for (int i = 0; i < FD_MAX; i++)
+    {
+        auto& descriptor = current->fd_table[i];
+        if (descriptor->flags & O_CLOEXEC) descriptor = {};
+    }
 
     MMU::delete_userspace_page_directory(current->directory);
 
diff --git a/kernel/src/sys/open.cpp b/kernel/src/sys/open.cpp
index 5aaaf1cf..4456bec9 100644
--- a/kernel/src/sys/open.cpp
+++ b/kernel/src/sys/open.cpp
@@ -7,7 +7,7 @@
 #include <bits/open-flags.h>
 
 // These flags are needed after open(), the rest only affect open().
-constexpr int FLAGS_TO_KEEP = O_RDWR | O_APPEND | O_NONBLOCK;
+constexpr int FLAGS_TO_KEEP = O_RDWR | O_APPEND | O_NONBLOCK | O_CLOEXEC;
 
 Result<u64> sys_open(Registers*, SyscallArgs args)
 {
diff --git a/libc/include/bits/open-flags.h b/libc/include/bits/open-flags.h
index e51b0547..c0f7e680 100644
--- a/libc/include/bits/open-flags.h
+++ b/libc/include/bits/open-flags.h
@@ -11,5 +11,6 @@
 #define O_EXCL 16
 #define O_TRUNC 32
 #define O_NONBLOCK 64
+#define O_CLOEXEC 128
 
 #endif