diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 553add1eb457..db2b10c718ba 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -3169,6 +3169,10 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
 
 	expr->operands[0] = operand1;
 	expr->operands[1] = operand2;
+
+	/* The operand sizes should be the same, so just pick one */
+	expr->size = operand1->size;
+
 	expr->operator = field_op;
 	expr->name = expr_str(expr, 0);
 	expr->type = kstrdup(operand1->type, GFP_KERNEL);