diff --git a/dnscache.c b/dnscache.c
index 8c899a3..8b10571 100644
--- a/dnscache.c
+++ b/dnscache.c
@@ -51,6 +51,7 @@ static char myipincoming[4];
 static char buf[1024];
 uint64 numqueries = 0;
 
+static unsigned int truncate_len = 512;
 
 static int udp53;
 
@@ -77,7 +78,7 @@ void u_respond(int j)
 {
   if (!u[j].active) return;
   response_id(u[j].id);
-  if (response_len > 512) response_tc();
+  if (response_len > truncate_len) response_tc();
   socket_send4(udp53,response,response_len,u[j].ip,u[j].port);
   log_querydone(&u[j].active,response_len);
   u[j].active = 0; --uactive;
@@ -431,6 +432,15 @@ int main()
   if (!cache_init(cachesize))
     strerr_die3x(111,FATAL,"not enough memory for cache of size ",x);
 
+  x = env_get("TRUNCATELEN");
+  if (x) {
+    scan_ulong(x,&truncate_len);
+    if (truncate_len < 512)
+      truncate_len = 512;
+    if (truncate_len > 16384)
+      truncate_len = 16384;
+  }
+
   if (env_get("HIDETTL"))
     response_hidettl();
   if (env_get("FORWARDONLY"))
diff --git a/server.c b/server.c
index e486fe1..63ad11c 100644
--- a/server.c
+++ b/server.c
@@ -2,6 +2,7 @@
 #include "case.h"
 #include "env.h"
 #include "buffer.h"
+#include "scan.h"
 #include "strerr.h"
 #include "ip4.h"
 #include "uint16.h"
@@ -83,6 +84,7 @@ int main()
 {
   char *x;
   int udp53;
+  unsigned int truncate_len = 512;
 
   x = env_get("IP");
   if (!x)
@@ -105,11 +107,19 @@ int main()
 
   buffer_putsflush(buffer_2,starting);
 
+  x = env_get("TRUNCATELEN");
+  if (x) {
+    scan_ulong(x,&truncate_len);
+    if (truncate_len < 512)
+      truncate_len = 512;
+    if (truncate_len > 16384)
+      truncate_len = 16384;
+  }
   for (;;) {
     len = socket_recv4(udp53,buf,sizeof buf,ip,&port);
     if (len < 0) continue;
     if (!doit()) continue;
-    if (response_len > 512) response_tc();
+    if (response_len > truncate_len) response_tc();
     socket_send4(udp53,response,response_len,ip,port);
     /* may block for buffer space; if it fails, too bad */
   }