diff --git a/src/main/scala/rocket/RocketCore.scala b/src/main/scala/rocket/RocketCore.scala
index 1eaf009e2c..ee3cec6f75 100644
--- a/src/main/scala/rocket/RocketCore.scala
+++ b/src/main/scala/rocket/RocketCore.scala
@@ -1118,7 +1118,7 @@ class Rocket(tile: RocketTile)(implicit p: Parameters) extends CoreModule()(p)
   io.dmem.req.bits.data := DontCare
   io.dmem.req.bits.mask := DontCare
 
-  io.dmem.s1_data.data := (if (fLen == 0) mem_reg_rs2 else Mux(mem_ctrl.fp, Fill((xLen max fLen) / fLen, io.fpu.store_data), mem_reg_rs2))
+  io.dmem.s1_data.data := (if (fLen == 0) mem_reg_rs2 else Mux(mem_ctrl.fp, Fill(coreDataBits / fLen, io.fpu.store_data), mem_reg_rs2))
   io.dmem.s1_data.mask := DontCare
 
   io.dmem.s1_kill := killm_common || mem_ldst_xcpt || fpu_kill_mem || vec_kill_mem