diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -464,7 +464,7 @@
 static void checkZOptions(opt::InputArgList &args) {
   for (auto *arg : args.filtered(OPT_z))
     if (!isKnownZFlag(arg->getValue()))
-      error("unknown -z value: " + StringRef(arg->getValue()));
+      warn("unknown -z value: " + StringRef(arg->getValue()));
 }
 
 void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
diff --git a/lld/test/ELF/driver.test b/lld/test/ELF/driver.test
--- a/lld/test/ELF/driver.test
+++ b/lld/test/ELF/driver.test
@@ -58,12 +58,12 @@
 # RUN: not ld.lld %t -output=/no/such/file 2>&1 | FileCheck -check-prefix=ERR9 %s
 # ERR9: cannot open output file utput=/no/such/file
 
-# RUN: not ld.lld %t -z foo 2>&1 | FileCheck -check-prefix=ERR10 %s
-# RUN: not ld.lld %t -z foo --version 2>&1 | FileCheck -check-prefix=ERR10 %s
-# ERR10: unknown -z value: foo
+# RUN: ld.lld %t -z foo 2>&1 | FileCheck -check-prefix=ERR10 %s
+# RUN: ld.lld %t -z foo --version 2>&1 | FileCheck -check-prefix=ERR10 %s
+# ERR10: warning: unknown -z value: foo
 
 ## Check we report "unknown -z value" error even with -v.
-# RUN: not ld.lld %t -z foo -v 2>&1 | FileCheck -check-prefix=ERR10 %s
+# RUN: ld.lld %t -z foo -v 2>&1 | FileCheck -check-prefix=ERR10 %s
 
 # RUN: not ld.lld %t -z max-page-size 2>&1 | FileCheck -check-prefix=ERR11 %s
 # ERR11: unknown -z value: max-page-size