diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 8d620a7..61c6b37 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -1164,7 +1164,21 @@
 
       SmallVector<DeclarationName,8> UnhandledNames;
 
-      for (EI = EnumVals.begin(); EI != EIEnd; EI++){
+      for (EI = EnumVals.begin(); EI != EIEnd; EI++) {
+        // Don't warn about omitted unavailable EnumConstantDecls.
+        switch (EI->second->getAvailability()) {
+        case AR_Deprecated:
+          // Omitting a deprecated constant is ok; it should never materialize.
+        case AR_Unavailable:
+          continue;
+
+        case AR_NotYetIntroduced:
+          // Partially available enum constants should be present. Note that we
+          // suppress -Wunguarded-availability diagnostics for such uses.
+        case AR_Available:
+          break;
+        }
+
         // Drop unneeded case values
         while (CI != CaseVals.end() && CI->first < EI->first)
           CI++;