diff --git a/src/Base64.cpp b/src/Base64.cpp
index 643cb2d70b..b4bdbd962f 100644
--- a/src/Base64.cpp
+++ b/src/Base64.cpp
@@ -91,7 +91,7 @@ static const unsigned char pr2six[256] =
 std::size_t Base64Decode(llvm::StringRef encoded, std::string* plain) {
   const unsigned char *bufin = encoded.bytes_begin();
   while (pr2six[*bufin] <= 63 && bufin != encoded.bytes_end()) ++bufin;
-  std::size_t nprbytes = (bufin - encoded.bytes_begin()) - 1;
+  std::size_t nprbytes = bufin - encoded.bytes_begin();
   std::size_t nbytesdecoded = ((nprbytes + 3) / 4) * 3;
 
   plain->clear();
@@ -121,18 +121,21 @@ static const char basis_64[] =
 
 void Base64Encode(llvm::StringRef plain, std::string* encoded) {
   encoded->clear();
+  if (plain.empty())
+    return;
   std::size_t len = plain.size();
   encoded->reserve(((len + 2) / 3 * 4) + 1);
 
-  std::size_t i;
-  for (i = 0; i < len - 2; i += 3) {
-    (*encoded) += basis_64[(plain[i] >> 2) & 0x3F];
-    (*encoded) +=
-        basis_64[((plain[i] & 0x3) << 4) | ((int)(plain[i + 1] & 0xF0) >> 4)];
-    (*encoded) += basis_64[((plain[i + 1] & 0xF) << 2) |
-                           ((int)(plain[i + 2] & 0xC0) >> 6)];
-    (*encoded) += basis_64[plain[i + 2] & 0x3F];
-  }
+  std::size_t i = 0;
+  if (len >= 2)
+    for (; i < len - 2; i += 3) {
+      (*encoded) += basis_64[(plain[i] >> 2) & 0x3F];
+      (*encoded) +=
+          basis_64[((plain[i] & 0x3) << 4) | ((int)(plain[i + 1] & 0xF0) >> 4)];
+      (*encoded) += basis_64[((plain[i + 1] & 0xF) << 2) |
+                             ((int)(plain[i + 2] & 0xC0) >> 6)];
+      (*encoded) += basis_64[plain[i + 2] & 0x3F];
+    }
   if (i < len) {
     (*encoded) += basis_64[(plain[i] >> 2) & 0x3F];
     if (i == (len - 1)) {
diff --git a/test/unit/test_Base64.cpp b/test/unit/test_Base64.cpp
new file mode 100644
index 0000000000..5f74cdebf2
--- /dev/null
+++ b/test/unit/test_Base64.cpp
@@ -0,0 +1,62 @@
+#include "Base64.h"
+
+#include "gtest/gtest.h"
+
+namespace ntimpl {
+
+struct Base64TestParam {
+  int plain_len;
+  const char* plain;
+  const char* encoded;
+};
+
+class Base64Test : public ::testing::TestWithParam<Base64TestParam> {
+ protected:
+  llvm::StringRef GetPlain() {
+    if (GetParam().plain_len < 0)
+      return llvm::StringRef(GetParam().plain);
+    else
+      return llvm::StringRef(GetParam().plain, GetParam().plain_len);
+  }
+};
+
+TEST_P(Base64Test, Encode) {
+  std::string s;
+  Base64Encode(GetPlain(), &s);
+  ASSERT_EQ(GetParam().encoded, s);
+}
+
+TEST_P(Base64Test, Decode) {
+  std::string s;
+  Base64Decode(GetParam().encoded, &s);
+  ASSERT_EQ(GetPlain(), s);
+}
+
+static Base64TestParam sample[] = {
+    {-1, "Send reinforcements", "U2VuZCByZWluZm9yY2VtZW50cw=="},
+    {-1, "Now is the time for all good coders\n to learn C++",
+     "Tm93IGlzIHRoZSB0aW1lIGZvciBhbGwgZ29vZCBjb2RlcnMKIHRvIGxlYXJuIEMrKw=="},
+    {-1,
+     "This is line one\nThis is line two\nThis is line three\nAnd so on...\n",
+     "VGhpcyBpcyBsaW5lIG9uZQpUaGlzIGlzIGxpbmUgdHdvClRoaXMgaXMgbGluZSB0aHJlZQpBb"
+     "mQgc28gb24uLi4K"},
+};
+
+INSTANTIATE_TEST_CASE_P(Base64Sample, Base64Test,
+                        ::testing::ValuesIn(sample));
+
+static Base64TestParam standard[] = {
+    {0, "", ""},
+    {1, "\0", "AA=="},
+    {2, "\0\0", "AAA="},
+    {3, "\0\0\0", "AAAA"},
+    {1, "\377", "/w=="},
+    {2, "\377\377", "//8="},
+    {3, "\377\377\377", "////"},
+    {2, "\xff\xef", "/+8="},
+};
+
+INSTANTIATE_TEST_CASE_P(Base64Standard, Base64Test,
+                        ::testing::ValuesIn(standard));
+ 
+}  // namespace ntimpl