diff --git a/sys/dev/em/if_em.c b/sys/dev/em/if_em.c
index 0033c501d850..a477cf0ac344 100644
--- a/sys/dev/em/if_em.c
+++ b/sys/dev/em/if_em.c
@@ -2579,7 +2579,7 @@ em_allocate_transmit_structures(struct adapter *adapter)
 	if ((adapter->hw.mac_type > em_82544) &&
 	    (adapter->hw.mac_type != em_82547)) {
 		size = EM_TSO_SIZE;
-		segsize = 4096; /* page size isn't always 4k */
+		segsize = EM_TSO_PCIE_SEGMENT_SIZE;
 	}
 
 	if ((error = bus_dma_tag_create(bus_get_dma_tag(dev),	/* parent */
diff --git a/sys/dev/em/if_em.h b/sys/dev/em/if_em.h
index 54b3f1d3431d..42b85a5bc027 100644
--- a/sys/dev/em/if_em.h
+++ b/sys/dev/em/if_em.h
@@ -181,6 +181,12 @@ POSSIBILITY OF SUCH DAMAGE.
  */
 /* #define EM_MASTER_SLAVE      2 */
 
+
+/*
+ * Limitation of some PCIe chipsets when using TSO
+ */
+#define EM_TSO_PCIE_SEGMENT_SIZE        4096
+
 /* Tunables -- End */
 
 #define AUTONEG_ADV_DEFAULT             (ADVERTISE_10_HALF | ADVERTISE_10_FULL | \