diff --git a/tcg/optimize.c b/tcg/optimize.c
index 627a5b39f6..b875d76354 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -46,6 +46,7 @@ typedef struct TempOptInfo {
 
 typedef struct OptContext {
     TCGContext *tcg;
+    TCGOp *prev_mb;
     TCGTempSet temps_used;
 } OptContext;
 
@@ -609,7 +610,7 @@ static bool swap_commutative2(TCGArg *p1, TCGArg *p2)
 void tcg_optimize(TCGContext *s)
 {
     int nb_temps, nb_globals, i;
-    TCGOp *op, *op_next, *prev_mb = NULL;
+    TCGOp *op, *op_next;
     OptContext ctx = { .tcg = s };
 
     /* Array VALS has an element for each temp.
@@ -1566,7 +1567,7 @@ void tcg_optimize(TCGContext *s)
         }
 
         /* Eliminate duplicate and redundant fence instructions.  */
-        if (prev_mb) {
+        if (ctx.prev_mb) {
             switch (opc) {
             case INDEX_op_mb:
                 /* Merge two barriers of the same type into one,
@@ -1580,7 +1581,7 @@ void tcg_optimize(TCGContext *s)
                  * barrier.  This is stricter than specified but for
                  * the purposes of TCG is better than not optimizing.
                  */
-                prev_mb->args[0] |= op->args[0];
+                ctx.prev_mb->args[0] |= op->args[0];
                 tcg_op_remove(s, op);
                 break;
 
@@ -1597,11 +1598,11 @@ void tcg_optimize(TCGContext *s)
             case INDEX_op_qemu_st_i64:
             case INDEX_op_call:
                 /* Opcodes that touch guest memory stop the optimization.  */
-                prev_mb = NULL;
+                ctx.prev_mb = NULL;
                 break;
             }
         } else if (opc == INDEX_op_mb) {
-            prev_mb = op;
+            ctx.prev_mb = op;
         }
     }
 }