diff --git a/src/DynareBison.yy b/src/DynareBison.yy
index 0085727669d9ec0597ddb49ab3633790d152f82b..687a85b9b998ea000f4a4b39d5318735e1b7b020 100644
--- a/src/DynareBison.yy
+++ b/src/DynareBison.yy
@@ -172,7 +172,7 @@ class ParsingDriver;
 %token PARAMETER_CONVERGENCE_CRITERION NUMBER_OF_LARGE_PERTURBATIONS NUMBER_OF_SMALL_PERTURBATIONS
 %token NUMBER_OF_POSTERIOR_DRAWS_AFTER_PERTURBATION MAX_NUMBER_OF_STAGES
 %token RANDOM_FUNCTION_CONVERGENCE_CRITERION RANDOM_PARAMETER_CONVERGENCE_CRITERION NO_INIT_ESTIMATION_CHECK_FIRST_OBS
-%token HETEROSKEDASTIC_FILTER TIME_SHIFT STRUCTURAL TERMINAL_STEADY_STATE_AS_GUESS_VALUE
+%token HETEROSKEDASTIC_FILTER TIME_SHIFT STRUCTURAL TERMINAL_STEADY_STATE_AS_GUESS_VALUE CONSTANT_SIMULATION_LENGTH
 %token SURPRISE OCCBIN_CONSTRAINTS
 %token PAC_TARGET_INFO COMPONENT TARGET AUXNAME AUXNAME_TARGET_NONSTATIONARY PAC_TARGET_NONSTATIONARY
 %token <string> KIND LL DL DD
@@ -1472,6 +1472,7 @@ perfect_foresight_with_expectation_errors_solver_options_list : perfect_foresigh
                                                               ;
 
 perfect_foresight_with_expectation_errors_solver_options : o_pfwee_terminal_steady_state_as_guess_value
+                                                         | o_pfwee_constant_simulation_length
                                                          | perfect_foresight_solver_options
                                                          ;
 
@@ -4046,6 +4047,7 @@ o_icd_colormap : COLORMAP EQUAL symbol { driver.option_num("initial_condition_de
 o_no_init_estimation_check_first_obs : NO_INIT_ESTIMATION_CHECK_FIRST_OBS { driver.option_num("no_init_estimation_check_first_obs", "true"); };
 o_heteroskedastic_filter : HETEROSKEDASTIC_FILTER { driver.option_num("heteroskedastic_filter", "true"); };
 o_pfwee_terminal_steady_state_as_guess_value : TERMINAL_STEADY_STATE_AS_GUESS_VALUE { driver.option_num("pfwee.terminal_steady_state_as_guess_value", "true"); };
+o_pfwee_constant_simulation_length : CONSTANT_SIMULATION_LENGTH { driver.option_num("pfwee.constant_simulation_length", "true"); };
 
 // Some options to "method_of_moments"
 o_bartlett_kernel_lag : BARTLETT_KERNEL_LAG EQUAL INT_NUMBER { driver.option_num("mom.bartlett_kernel_lag", $3); };
diff --git a/src/DynareFlex.ll b/src/DynareFlex.ll
index 17167d0426f270d9ec83e3a4318549b8448ff14d..8c9e15a651bc0662c663a32a3317f045c3cf8c02 100644
--- a/src/DynareFlex.ll
+++ b/src/DynareFlex.ll
@@ -877,6 +877,7 @@ DATE -?[0-9]+([ya]|m([1-9]|1[0-2])|q[1-4])
 <DYNARE_STATEMENT>no_homotopy {return token::NO_HOMOTOPY;}
 <DYNARE_STATEMENT>particle_filter_options {return token::PARTICLE_FILTER_OPTIONS;}
 <DYNARE_STATEMENT>terminal_steady_state_as_guess_value {return token::TERMINAL_STEADY_STATE_AS_GUESS_VALUE;}
+<DYNARE_STATEMENT>constant_simulation_length {return token::CONSTANT_SIMULATION_LENGTH;}
 <DYNARE_STATEMENT>static { return token::STATIC; }
 <DYNARE_STATEMENT>incidence { return token::INCIDENCE; }