diff --git a/lib/CppInterOp/CppInterOp.cpp b/lib/CppInterOp/CppInterOp.cpp
index 90c934d19..b832f3d73 100644
--- a/lib/CppInterOp/CppInterOp.cpp
+++ b/lib/CppInterOp/CppInterOp.cpp
@@ -793,7 +793,11 @@ TCppIndex_t GetEnumConstantValue(TCppScope_t handle) {
   auto* D = (clang::Decl*)handle;
   if (auto* ECD = llvm::dyn_cast_or_null<clang::EnumConstantDecl>(D)) {
     const llvm::APSInt& Val = ECD->getInitVal();
-    return INTEROP_RETURN(Val.getExtValue());
+    if (Val.isRepresentableByInt64())
+      return INTEROP_RETURN(Val.getExtValue());
+    llvm::SmallString<40> StrVal;
+    Val.toString(StrVal);
+    return INTEROP_RETURN(std::stoul(StrVal.c_str()));
   }
   return INTEROP_RETURN(0);
 }
diff --git a/unittests/CppInterOp/EnumReflectionTest.cpp b/unittests/CppInterOp/EnumReflectionTest.cpp
index 19b58f3e7..c1c74e884 100644
--- a/unittests/CppInterOp/EnumReflectionTest.cpp
+++ b/unittests/CppInterOp/EnumReflectionTest.cpp
@@ -238,6 +238,10 @@ TYPED_TEST(CPPINTEROP_TEST_MODE, EnumReflection_GetEnumConstantValue) {
       MinusNine
     };
     int a = 10;
+
+    enum TooLong : unsigned long long {
+      BIG = ((unsigned long long)1)<<63
+    };
   )";
 
   GetAllTopLevelDecls(code, Decls);
@@ -250,7 +254,12 @@ TYPED_TEST(CPPINTEROP_TEST_MODE, EnumReflection_GetEnumConstantValue) {
   EXPECT_EQ(Cpp::GetEnumConstantValue(EnumConstants[4]), 54);
   EXPECT_EQ(Cpp::GetEnumConstantValue(EnumConstants[5]), -10);
   EXPECT_EQ(Cpp::GetEnumConstantValue(EnumConstants[6]), -9);
+
   EXPECT_EQ(Cpp::GetEnumConstantValue(Decls[1]), 0); // Checking value of non enum constant
+
+  EnumConstants = Cpp::GetEnumConstants(Decls[2]);
+  EXPECT_EQ(Cpp::GetEnumConstantValue(EnumConstants[0]), ((unsigned long long)1)
+                                                             << 63);
 }
 
 TYPED_TEST(CPPINTEROP_TEST_MODE, EnumReflection_GetEnums) {