diff --git a/sys/dev/cxgbe/common/t4_hw.c b/sys/dev/cxgbe/common/t4_hw.c
index 8d109b389f0..755062909e1 100644
--- a/sys/dev/cxgbe/common/t4_hw.c
+++ b/sys/dev/cxgbe/common/t4_hw.c
@@ -6742,7 +6742,7 @@ static unsigned int t4_get_mps_bg_map(struct adapter *adap, int idx)
 {
 	u32 n;
 
-	if (adap->params.mps_bg_map)
+	if (adap->params.mps_bg_map != UINT32_MAX)
 		return ((adap->params.mps_bg_map >> (idx << 3)) & 0xff);
 
 	n = adap->params.nports;
diff --git a/sys/dev/cxgbe/t4_main.c b/sys/dev/cxgbe/t4_main.c
index b41746828e9..4834a4fc287 100644
--- a/sys/dev/cxgbe/t4_main.c
+++ b/sys/dev/cxgbe/t4_main.c
@@ -5333,7 +5333,7 @@ get_params__post_init(struct adapter *sc)
 	if (rc == 0)
 		sc->params.mps_bg_map = val[0];
 	else
-		sc->params.mps_bg_map = 0;
+		sc->params.mps_bg_map = UINT32_MAX;	/* Not a legal value. */
 
 	/*
 	 * Determine whether the firmware supports the filter2 work request.