diff --git a/lib/Support/StringRef.cpp b/lib/Support/StringRef.cpp
index 7503fac240a..51e0394d8bd 100644
--- a/lib/Support/StringRef.cpp
+++ b/lib/Support/StringRef.cpp
@@ -351,6 +351,9 @@ size_t StringRef::count(StringRef Str) const {
 }
 
 static unsigned GetAutoSenseRadix(StringRef &Str) {
+  if (Str.empty())
+    return 10;
+
   if (Str.startswith("0x") || Str.startswith("0X")) {
     Str = Str.substr(2);
     return 16;
diff --git a/unittests/ADT/StringRefTest.cpp b/unittests/ADT/StringRefTest.cpp
index 4249f231481..40ab4e038b8 100644
--- a/unittests/ADT/StringRefTest.cpp
+++ b/unittests/ADT/StringRefTest.cpp
@@ -571,7 +571,8 @@ TEST(StringRefTest, getAsInteger) {
 
 
 static const char* BadStrings[] = {
-    "18446744073709551617"  // value just over max
+    ""                      // empty string
+  , "18446744073709551617"  // value just over max
   , "123456789012345678901" // value way too large
   , "4t23v"                 // illegal decimal characters
   , "0x123W56"              // illegal hex characters