diff --git a/compiler/GHC/CmmToAsm/Reg/Liveness.hs b/compiler/GHC/CmmToAsm/Reg/Liveness.hs
index d3c8b261b5d35dd74be4f6a2c969596659bac068..90fbeb06a258e17c08ca87c7e103a05b36cb1007 100644
--- a/compiler/GHC/CmmToAsm/Reg/Liveness.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Liveness.hs
@@ -1001,7 +1001,7 @@ livenessBack
 livenessBack _        liveregs _        done []  = (liveregs, done)
 
 livenessBack platform liveregs blockmap acc (instr : instrs)
- = let  (liveregs', instr')     = liveness1 platform liveregs blockmap instr
+ = let  !(!liveregs', instr')     = liveness1 platform liveregs blockmap instr
    in   livenessBack platform liveregs' blockmap (instr' : acc) instrs