diff --git a/include/swift/SIL/SILBasicBlock.h b/include/swift/SIL/SILBasicBlock.h
index d582b76509dee..22438ec3fac27 100644
--- a/include/swift/SIL/SILBasicBlock.h
+++ b/include/swift/SIL/SILBasicBlock.h
@@ -153,7 +153,9 @@ public SwiftObjectHeader {
   ~SILBasicBlock();
 
   enum { numCustomBits = std::numeric_limits<CustomBitsType>::digits };
-  enum { maxBitfieldID = std::numeric_limits<uint64_t>::max() };
+
+  constexpr static const size_t maxBitfieldID =
+      std::numeric_limits<uint64_t>::max();
 
   /// Gets the ID (= index in the function's block list) of the block.
   ///
diff --git a/include/swift/SIL/SILNode.h b/include/swift/SIL/SILNode.h
index ebfa18af953cd..cd62e83723858 100644
--- a/include/swift/SIL/SILNode.h
+++ b/include/swift/SIL/SILNode.h
@@ -127,7 +127,9 @@ class alignas(8) SILNode :
   enum { NumMarkDependenceKindBits = 2 };
 
   enum { numCustomBits = 20 };
-  enum { maxBitfieldID = std::numeric_limits<uint64_t>::max() >> numCustomBits };
+
+  constexpr static const size_t maxBitfieldID =
+      std::numeric_limits<uint64_t>::max() >> numCustomBits;
 
 protected:
   friend class SILInstruction;
diff --git a/include/swift/SIL/SILValue.h b/include/swift/SIL/SILValue.h
index 3d04109af7b44..1e6e118164500 100644
--- a/include/swift/SIL/SILValue.h
+++ b/include/swift/SIL/SILValue.h
@@ -1021,7 +1021,9 @@ ValueOwnershipKind::getForwardingOperandOwnership(bool allowUnowned) const {
 class Operand {
 public:
   enum { numCustomBits = 8 };
-  enum { maxBitfieldID = std::numeric_limits<uint64_t>::max() >> numCustomBits };
+
+  constexpr static const size_t maxBitfieldID =
+      std::numeric_limits<uint64_t>::max() >> numCustomBits;
 
 private:
   template <class, class> friend class SILBitfield;