diff --git a/gen/toir.cpp b/gen/toir.cpp
index 84a9dca6..10dff631 100644
--- a/gen/toir.cpp
+++ b/gen/toir.cpp
@@ -11,6 +11,7 @@
 #include <fstream>
 
 #include "gen/llvm.h"
+#include "llvm/Support/DataTypes.h"
 
 #include "attrib.h"
 #include "init.h"
@@ -314,7 +315,7 @@ DValue* RealExp::toElem(IRState* p)
 LLConstant* RealExp::toConstElem(IRState* p)
 {
     Logger::print("RealExp::toConstElem: %s @ %s | %LX\n", toChars(), type->toChars(),
-        0xFFFFFFFFFFUL & *(long long unsigned*)&value);
+        UINT64_C(0xFFFFFFFFFF) & *(long long unsigned*)&value);
     LOG_SCOPE;
     Type* t = type->toBasetype();
     return DtoConstFP(t, value);