diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5645,9 +5645,9 @@
                        (RTTIMode == ToolChain::RM_Disabled)))
     CmdArgs.push_back("-fno-rtti");
 
-  // -fshort-enums=0 is default for all architectures except Hexagon.
+  // -fshort-enums=0 is default for all architectures except Hexagon and z/OS.
   if (Args.hasFlag(options::OPT_fshort_enums, options::OPT_fno_short_enums,
-                   TC.getArch() == llvm::Triple::hexagon))
+                   TC.getArch() == llvm::Triple::hexagon || Triple.isOSzOS()))
     CmdArgs.push_back("-fshort-enums");
 
   RenderCharacterOptions(Args, AuxTriple ? *AuxTriple : RawTriple, CmdArgs);
diff --git a/clang/test/Driver/zos-driver-defaults.c b/clang/test/Driver/zos-driver-defaults.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/zos-driver-defaults.c
@@ -0,0 +1,9 @@
+// RUN: %clang -### --target=s390x-none-zos -fsyntax-only %s 2>&1 | FileCheck --check-prefix=CHECK-SHORT-ENUMS %s
+// RUN: %clang -### --target=s390x-none-zos -fno-short-enums -fsyntax-only %s 2>&1 | FileCheck %s
+// REQUIRES: clang-driver
+
+//CHECK-SHORT-ENUMS: -fshort-enums
+//CHECK-SHORT-ENUMS: -fno-signed-char
+
+//CHECK-NOT: -fshort-enums
+//CHECK: -fno-signed-char