diff --git a/src/d_net.cpp b/src/d_net.cpp
index 6e2877495..dfee7460e 100644
--- a/src/d_net.cpp
+++ b/src/d_net.cpp
@@ -1173,7 +1173,7 @@ void NetUpdate (void)
 			netbuffer[k++] = lowtic;
 		}
 
-		numtics = lowtic - realstart;
+		numtics = MAX(0, lowtic - realstart);
 		if (numtics > BACKUPTICS)
 			I_Error ("NetUpdate: Node %d missed too many tics", i);
 
diff --git a/src/i_net.cpp b/src/i_net.cpp
index e03c2c0e8..3ec9d7881 100644
--- a/src/i_net.cpp
+++ b/src/i_net.cpp
@@ -208,11 +208,11 @@ void PacketSend (void)
 	{
 		I_FatalError("Netbuffer overflow!");
 	}
+	assert(!(doomcom.data[0] & NCMD_COMPRESSED));
 
 	uLong size = TRANSMIT_SIZE - 1;
 	if (doomcom.datalength >= 10)
 	{
-		assert(!(doomcom.data[0] & NCMD_COMPRESSED));
 		TransmitBuffer[0] = doomcom.data[0] | NCMD_COMPRESSED;
 		c = compress2(TransmitBuffer + 1, &size, doomcom.data + 1, doomcom.datalength - 1, 9);
 		size += 1;