diff --git a/openair1/PHY/LTE_TRANSPORT/if4_tools.c b/openair1/PHY/LTE_TRANSPORT/if4_tools.c
index 56799ea894a6ec6d01a1a573e3debba9b79a9cc0..2afb6ff019005143618cac4182ebdec4e94cef15 100755
--- a/openair1/PHY/LTE_TRANSPORT/if4_tools.c
+++ b/openair1/PHY/LTE_TRANSPORT/if4_tools.c
@@ -150,7 +150,7 @@ void send_IF4p5(PHY_VARS_eNB *eNB, int frame, int subframe, uint16_t packet_type
   } else if (packet_type == IF4p5_PRACH) {
     // FIX: hard coded prach samples length
     LOG_D(PHY,"IF4p5_PRACH: frame %d, subframe %d\n",frame,subframe);
-    db_fulllength = 840*2;
+    db_fulllength = PRACH_HARD_CODED_SIZE;
     if (eth->flags == ETH_RAW_IF4p5_MODE) {
       packet_header = (IF4p5_header_t *)(tx_buffer + MAC_HEADER_SIZE_BYTES);
       data_block = (uint16_t*)(tx_buffer + MAC_HEADER_SIZE_BYTES + sizeof_IF4p5_header_t);
diff --git a/targets/ARCH/ETHERNET/USERSPACE/LIB/if_defs.h b/targets/ARCH/ETHERNET/USERSPACE/LIB/if_defs.h
index 855ff4970438b774fc5865407a6b47315ff690b8..c06656f2dc8a712624cfcb4ec256062bd09793e4 100644
--- a/targets/ARCH/ETHERNET/USERSPACE/LIB/if_defs.h
+++ b/targets/ARCH/ETHERNET/USERSPACE/LIB/if_defs.h
@@ -60,7 +60,8 @@
 
 // Packet sizes for IF4p5 interface format
 #define DATA_BLOCK_SIZE_BYTES(scaled_nblocks) (sizeof(uint16_t)*scaled_nblocks)
-#define PRACH_BLOCK_SIZE_BYTES (sizeof(int16_t)*839*2)  // FIX hard coded prach size (uncompressed)
+#define PRACH_HARD_CODED_SIZE (839*2)
+#define PRACH_BLOCK_SIZE_BYTES (sizeof(int16_t)*PRACH_HARD_CODED_SIZE)  // FIX hard coded prach size
  
 #define RAW_IF4p5_PDLFFT_SIZE_BYTES(nblocks) (MAC_HEADER_SIZE_BYTES + sizeof_IF4p5_header_t + DATA_BLOCK_SIZE_BYTES(nblocks))  
 #define RAW_IF4p5_PULFFT_SIZE_BYTES(nblocks) (MAC_HEADER_SIZE_BYTES + sizeof_IF4p5_header_t + DATA_BLOCK_SIZE_BYTES(nblocks))