Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -1783,6 +1783,9 @@
       }
     }
     for (const auto *I : RD->fields()) {
+      if (I->isUnnamedBitfield())
+        continue;
+
       if (!CheckConstantExpression(Info, DiagLoc, I->getType(),
                                    Value.getStructField(I->getFieldIndex())))
         return false;
Index: test/SemaCXX/constant-expression-cxx11.cpp
===================================================================
--- test/SemaCXX/constant-expression-cxx11.cpp
+++ test/SemaCXX/constant-expression-cxx11.cpp
@@ -1920,6 +1920,23 @@
     };
     static_assert(X::f(3) == -1, "3 should truncate to -1");
   }
+
+
+  struct HasUnnamedBitfield {
+    unsigned a;
+    unsigned : 20;
+    unsigned b;
+
+    constexpr HasUnnamedBitfield() : a(), b() {}
+    constexpr HasUnnamedBitfield(unsigned a, unsigned b) : a(a), b(b) {}
+  };
+
+  void testUnnamedBitfield() {
+    const HasUnnamedBitfield zero{};
+    int a = 1 / zero.b; // expected-error {{division by zero is undefined}}
+    const HasUnnamedBitfield oneZero{1, 0};
+    int b = 1 / oneZero.b; // expected-error {{division by zero is undefined}}
+  }
 }
 
 namespace ZeroSizeTypes {
Index: test/SemaCXX/warn-global-constructors.cpp
===================================================================
--- test/SemaCXX/warn-global-constructors.cpp
+++ test/SemaCXX/warn-global-constructors.cpp
@@ -126,3 +126,22 @@
 void *array_storage[1];
 const int &global_reference = *(int *)array_storage;
 }
+
+namespace HasUnnamedBitfield {
+  struct HasUnnamedBitfield {
+    unsigned a;
+    unsigned : 20;
+    unsigned b;
+
+    constexpr HasUnnamedBitfield() : a(), b() {}
+    constexpr HasUnnamedBitfield(unsigned a, unsigned b) : a(a), b(b) {}
+    explicit HasUnnamedBitfield(unsigned a) {}
+  };
+
+  const HasUnnamedBitfield zeroConst{};
+  HasUnnamedBitfield zeroMutable{};
+  const HasUnnamedBitfield explicitConst{1, 2};
+  HasUnnamedBitfield explicitMutable{1, 2};
+  const HasUnnamedBitfield nonConstexprConst{1}; // expected-warning {{global constructor}}
+  HasUnnamedBitfield nonConstexprMutable{1}; // expected-warning {{global constructor}}
+}
\ No newline at end of file