diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index 6f4edc3..3663ed7 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -553,11 +553,24 @@
   addSubstitution(Template);
 }
 
-void CXXNameMangler::mangleFloat(const llvm::APFloat &F) {
-  // TODO: avoid this copy with careful stream management.
-  llvm::SmallString<20> Buffer;
-  F.bitcastToAPInt().toString(Buffer, 16, false);
-  Out.write(Buffer.data(), Buffer.size());
+void CXXNameMangler::mangleFloat(const llvm::APFloat &f) {
+  // ABI:
+  //   Floating-point literals are encoded using a fixed-length
+  //   lowercase hexadecimal string corresponding to the internal
+  //   representation (IEEE on Itanium), high-order bytes first,
+  //   without leading zeroes. For example: "Lf bf800000 E" is -1.0f
+  //   on Itanium.
+  // APInt::toString uses uppercase hexadecimal, and it's not really
+  // worth embellishing that interface for this use case, so we just
+  // do a second pass to lowercase things.
+  typedef llvm::SmallString<20> buffer_t;
+  buffer_t buffer;
+  f.bitcastToAPInt().toString(buffer, 16, false);
+
+  for (buffer_t::iterator i = buffer.begin(), e = buffer.end(); i != e; ++i)
+    if (isupper(*i)) *i = tolower(*i);
+
+  Out.write(buffer.data(), buffer.size());
 }
 
 void CXXNameMangler::mangleNumber(const llvm::APSInt &Value) {
diff --git a/test/CodeGenCXX/mangle.cpp b/test/CodeGenCXX/mangle.cpp
index 36bf7a8..54fb6a3 100644
--- a/test/CodeGenCXX/mangle.cpp
+++ b/test/CodeGenCXX/mangle.cpp
@@ -348,7 +348,7 @@
     char buffer[sizeof(float)];
     g<float>(buffer);
   }
-  // CHECK: define linkonce_odr void @_ZN5test01gIfEEvRAszplcvT__ELf40A00000E_c(
+  // CHECK: define linkonce_odr void @_ZN5test01gIfEEvRAszplcvT__ELf40a00000E_c(
 
   template <class T> void h(char (&buffer)[sizeof(T() + 5.0)]) {}
   void test3() {