diff --git a/src/arch/null/registers.hh b/src/arch/null/registers.hh
index 3d27d95a2d..5dd873222b 100644
--- a/src/arch/null/registers.hh
+++ b/src/arch/null/registers.hh
@@ -47,8 +47,8 @@
 namespace NullISA {
 
 typedef uint64_t IntReg;
-typedef uint32_t FloatRegBits;
-typedef float FloatReg;
+typedef uint64_t FloatRegBits;
+typedef double FloatReg;
 typedef uint8_t CCReg;
 typedef uint64_t MiscReg;
 const RegIndex ZeroReg = 0;