diff --git a/lib/Support/APFloat.cpp b/lib/Support/APFloat.cpp
index 5307829ed83..95df8617fb5 100644
--- a/lib/Support/APFloat.cpp
+++ b/lib/Support/APFloat.cpp
@@ -3243,8 +3243,9 @@ APFloat APFloat::getLargest(const fltSemantics &Sem, bool Negative) {
     significand[i] = ~((integerPart) 0);
 
   // ...and then clear the top bits for internal consistency.
-  significand[N-1] &=
-    (((integerPart) 1) << ((Sem.precision % integerPartWidth) - 1)) - 1;
+  if (Sem.precision % integerPartWidth != 0)
+    significand[N-1] &=
+      (((integerPart) 1) << (Sem.precision % integerPartWidth)) - 1;
 
   return Val;
 }
diff --git a/unittests/ADT/APFloatTest.cpp b/unittests/ADT/APFloatTest.cpp
index 3c40a13d367..e70c5f7af2b 100644
--- a/unittests/ADT/APFloatTest.cpp
+++ b/unittests/ADT/APFloatTest.cpp
@@ -648,4 +648,9 @@ TEST(APFloatTest, exactInverse) {
   EXPECT_FALSE(APFloat(1.40129846e-45f).getExactInverse(0));
 }
 
+TEST(APFloatTest, getLargest) {
+  EXPECT_EQ(3.40282347e+38f, APFloat::getLargest(APFloat::IEEEsingle).convertToFloat());
+  EXPECT_EQ(1.7976931348623157e+308, APFloat::getLargest(APFloat::IEEEdouble).convertToDouble());
+}
+
 }