diff --git a/lib/ExecutionEngine/ExecutionEngine.cpp b/lib/ExecutionEngine/ExecutionEngine.cpp
index 2cb4a8e..771ce0b 100644
--- a/lib/ExecutionEngine/ExecutionEngine.cpp
+++ b/lib/ExecutionEngine/ExecutionEngine.cpp
@@ -457,6 +457,8 @@
     case Type::IntegerTyID: {
       unsigned BitWidth = cast<IntegerType>(Ty)->getBitWidth();
       uint64_t BitMask = (1ull << BitWidth) - 1;
+      if (BitWidth >= 64)
+        BitMask = (uint64_t)-1;
       GenericValue TmpVal = Val;
       if (BitWidth <= 8)
         Ptr->Untyped[0] = Val.Int8Val & BitMask;
@@ -513,6 +515,8 @@
     case Type::IntegerTyID: {
       unsigned BitWidth = cast<IntegerType>(Ty)->getBitWidth();
       uint64_t BitMask = (1ull << BitWidth) - 1;
+      if (BitWidth >= 64)
+        BitMask = (uint64_t)-1;
       GenericValue TmpVal = Val;
       if (BitWidth <= 8)
         Ptr->Untyped[0] = Val.Int8Val & BitMask;