diff --git a/security/sandbox/linux/SandboxFilter.cpp b/security/sandbox/linux/SandboxFilter.cpp
index 20e9b59685..e053580992 100644
--- a/security/sandbox/linux/SandboxFilter.cpp
+++ b/security/sandbox/linux/SandboxFilter.cpp
@@ -1598,6 +1598,11 @@ class ContentSandboxPolicy : public SandboxPolicyCommon {
         // usually do something reasonable on error.
       case __NR_clone:
         return ClonePolicy(Error(EPERM));
+#  ifdef __NR_fork
+      case __NR_fork:
+        return Error(ENOSYS);
+#  endif
+
 
       case __NR_clone3:
         return Error(ENOSYS);