diff --git a/llvm/lib/Support/ConvertUTFWrapper.cpp b/llvm/lib/Support/ConvertUTFWrapper.cpp
--- a/llvm/lib/Support/ConvertUTFWrapper.cpp
+++ b/llvm/lib/Support/ConvertUTFWrapper.cpp
@@ -97,6 +97,8 @@
   const UTF16 *Src = reinterpret_cast<const UTF16 *>(SrcBytes.begin());
   const UTF16 *SrcEnd = reinterpret_cast<const UTF16 *>(SrcBytes.end());
 
+  assert((uintptr_t)Src % sizeof(UTF16) == 0);
+
   // Byteswap if necessary.
   std::vector<UTF16> ByteSwapped;
   if (Src[0] == UNI_UTF16_BYTE_ORDER_MARK_SWAPPED) {
diff --git a/llvm/unittests/Support/ConvertUTFTest.cpp b/llvm/unittests/Support/ConvertUTFTest.cpp
--- a/llvm/unittests/Support/ConvertUTFTest.cpp
+++ b/llvm/unittests/Support/ConvertUTFTest.cpp
@@ -16,7 +16,7 @@
 
 TEST(ConvertUTFTest, ConvertUTF16LittleEndianToUTF8String) {
   // Src is the look of disapproval.
-  static const char Src[] = "\xff\xfe\xa0\x0c_\x00\xa0\x0c";
+  alignas(UTF16) static const char Src[] = "\xff\xfe\xa0\x0c_\x00\xa0\x0c";
   ArrayRef<char> Ref(Src, sizeof(Src) - 1);
   std::string Result;
   bool Success = convertUTF16ToUTF8String(Ref, Result);
@@ -27,7 +27,7 @@
 
 TEST(ConvertUTFTest, ConvertUTF16BigEndianToUTF8String) {
   // Src is the look of disapproval.
-  static const char Src[] = "\xfe\xff\x0c\xa0\x00_\x0c\xa0";
+  alignas(UTF16) static const char Src[] = "\xfe\xff\x0c\xa0\x00_\x0c\xa0";
   ArrayRef<char> Ref(Src, sizeof(Src) - 1);
   std::string Result;
   bool Success = convertUTF16ToUTF8String(Ref, Result);
@@ -80,7 +80,7 @@
 
 TEST(ConvertUTFTest, UTF16WrappersForConvertUTF16ToUTF8String) {
   // Src is the look of disapproval.
-  static const char Src[] = "\xff\xfe\xa0\x0c_\x00\xa0\x0c";
+  alignas(UTF16) static const char Src[] = "\xff\xfe\xa0\x0c_\x00\xa0\x0c";
   ArrayRef<UTF16> SrcRef = makeArrayRef((const UTF16 *)Src, 4);
   std::string Result;
   bool Success = convertUTF16ToUTF8String(SrcRef, Result);