diff --git a/doc/dynare.texi b/doc/dynare.texi
index 23ddc0de247153dd1dcd7f62263343de37d294ad..67a7bd1a695723a8f25734d5ed83ccd0012be6b6 100644
--- a/doc/dynare.texi
+++ b/doc/dynare.texi
@@ -6829,6 +6829,12 @@ Metropolis has been run, @code{mle_mode} if MLE has been run.
 @xref{datafile}. Useful when computing the shock decomposition on a
 calibrated model.
 
+@item first_obs = @var{INTEGER}
+@xref{first_obs}.
+
+@item nobs = @var{INTEGER}
+@xref{nobs}.
+
 @item use_shock_groups [= @var{SHOCK_GROUPS_NAME}]
 @anchor{use_shock_groups}. Uses groups of shocks instead of individual shocks in
 the decomposition. Groups of shocks are defined in @xref{shock_groups} block.
diff --git a/preprocessor/DynareBison.yy b/preprocessor/DynareBison.yy
index fcd4def98243fce9c727435bb7e7c8739620c8af..2f103831a2cdff4f3a7a1fc24d92f2a852428ca9 100644
--- a/preprocessor/DynareBison.yy
+++ b/preprocessor/DynareBison.yy
@@ -2477,6 +2477,8 @@ shock_decomposition_option : o_parameter_set
                            | o_use_shock_groups
                            | o_colormap
                            | o_shock_decomposition_nograph
+                           | o_first_obs
+                           | o_nobs
                            ;
 
 homotopy_setup: HOMOTOPY_SETUP ';' homotopy_list END ';'