Index: lib/Sema/SemaStmt.cpp
===================================================================
--- lib/Sema/SemaStmt.cpp
+++ lib/Sema/SemaStmt.cpp
@@ -1162,6 +1162,9 @@
           break;
         }
 
+        if (EI->second->hasAttr<UnusedAttr>())
+          continue;
+
         // Drop unneeded case values
         while (CI != CaseVals.end() && CI->first < EI->first)
           CI++;
Index: test/CXX/dcl.dcl/dcl.attr/dcl.attr.unused/p3.cpp
===================================================================
--- test/CXX/dcl.dcl/dcl.attr/dcl.attr.unused/p3.cpp
+++ test/CXX/dcl.dcl/dcl.attr/dcl.attr.unused/p3.cpp
@@ -5,9 +5,17 @@
 
 struct [[maybe_unused]] S {};
 
+enum E1 {
+  EnumVal [[maybe_unused]],
+  UsedEnumVal,
+};
+
 void f() {
   int x; // expected-warning {{unused variable}}
   typedef int I; // expected-warning {{unused typedef 'I'}}
+  E1 e;
+  switch (e) { // expected-warning {{enumeration value 'UsedEnumVal' not handled in switch}}
+  }
 
   // Should not warn about these due to not being used.
   [[maybe_unused]] int y;
@@ -17,10 +25,16 @@
   S s;
   maybe_unused_int test;
   y = 12;
+  switch (e) {
+  case UsedEnumVal:
+    break;
+  }
 }
 
 #ifdef EXT
 // expected-warning@6 {{use of the 'maybe_unused' attribute is a C++17 extension}}
-// expected-warning@13 {{use of the 'maybe_unused' attribute is a C++17 extension}}
-// expected-warning@14 {{use of the 'maybe_unused' attribute is a C++17 extension}}
+// expected-warning@9 {{use of the 'maybe_unused' attribute is a C++17 extension}}
+// expected-warning@9 {{attributes on an enumerator declaration are a C++17 extension}}
+// expected-warning@21 {{use of the 'maybe_unused' attribute is a C++17 extension}}
+// expected-warning@22 {{use of the 'maybe_unused' attribute is a C++17 extension}}
 #endif