diff --git a/lib/include/srsran/phy/phch/prach.h b/lib/include/srsran/phy/phch/prach.h
index c5188a3e6..942c5aad5 100644
--- a/lib/include/srsran/phy/phch/prach.h
+++ b/lib/include/srsran/phy/phch/prach.h
@@ -170,6 +170,8 @@ SRSRAN_API bool srsran_prach_tti_opportunity(srsran_prach_t* p, uint32_t current
 SRSRAN_API bool
 srsran_prach_tti_opportunity_config_fdd(uint32_t config_idx, uint32_t current_tti, int allowed_subframe);
 
+SRSRAN_API bool srsran_prach_in_window_config_fdd(uint32_t config_idx, uint32_t current_tti, int allowed_subframe);
+
 SRSRAN_API bool srsran_prach_tti_opportunity_config_tdd(uint32_t  config_idx,
                                                         uint32_t  tdd_ul_dl_config,
                                                         uint32_t  current_tti,
diff --git a/lib/src/phy/phch/prach.c b/lib/src/phy/phch/prach.c
index 210561f55..bfbd84e0d 100644
--- a/lib/src/phy/phch/prach.c
+++ b/lib/src/phy/phch/prach.c
@@ -154,6 +154,23 @@ bool srsran_prach_tti_opportunity_config_fdd(uint32_t config_idx, uint32_t curre
   return false;
 }
 
+bool srsran_prach_in_window_config_fdd(uint32_t config_idx, uint32_t current_tti, int allowed_subframe)
+{
+  if (srsran_prach_tti_opportunity_config_fdd(config_idx, current_tti, allowed_subframe)) {
+    return true;
+  }
+
+  uint32_t preamble_format = srsran_prach_get_preamble_format(config_idx);
+  float    T_tot           = (prach_Tseq[preamble_format] + prach_Tcp[preamble_format]) * SRSRAN_LTE_TS;
+  uint32_t tti_dur         = (uint32_t)ceilf(T_tot * 1000);
+  for (uint32_t i = 1; i < tti_dur; ++i) {
+    if (srsran_prach_tti_opportunity_config_fdd(config_idx, current_tti - i, allowed_subframe)) {
+      return true;
+    }
+  }
+  return false;
+}
+
 uint32_t srsran_prach_nof_f_idx_tdd(uint32_t config_idx, uint32_t tdd_ul_dl_config)
 {
   if (config_idx < 64 && tdd_ul_dl_config < 7) {
diff --git a/srsenb/src/stack/mac/sched_grid.cc b/srsenb/src/stack/mac/sched_grid.cc
index 4b3813195..4f80f008f 100644
--- a/srsenb/src/stack/mac/sched_grid.cc
+++ b/srsenb/src/stack/mac/sched_grid.cc
@@ -99,7 +99,7 @@ void sf_grid_t::new_tti(tti_point tti_rx_)
   ul_mask |= pucch_mask;
 
   // Reserve PRBs for PRACH
-  if (srsran_prach_tti_opportunity_config_fdd(cc_cfg->cfg.prach_config, to_tx_ul(tti_rx).to_uint(), -1)) {
+  if (srsran_prach_in_window_config_fdd(cc_cfg->cfg.prach_config, to_tx_ul(tti_rx).to_uint(), -1)) {
     prbmask_t prach_mask{cc_cfg->nof_prb()};
     prach_mask.fill(cc_cfg->cfg.prach_freq_offset, cc_cfg->cfg.prach_freq_offset + 6);
     reserve_ul_prbs(prach_mask, false); // TODO: set to true once test sib.conf files are updated