diff --git a/src/xmppipe.c b/src/xmppipe.c
index ac58fcb..0a2a1a1 100644
--- a/src/xmppipe.c
+++ b/src/xmppipe.c
@@ -89,7 +89,7 @@ int main(int argc, char **argv) {
   state = xmppipe_calloc(1, sizeof(xmppipe_state_t));
 
   xmppipe_next_state(state, XMPPIPE_S_CONNECTING);
-  state->bufsz = 2049;
+  state->bufsz = -1;
   state->poll = 10;
   state->keepalive = 60 * 1000;
   state->keepalive_limit = 3;
@@ -240,6 +240,17 @@ int main(int argc, char **argv) {
     exit(2);
   }
 
+  if (state->bufsz == -1) {
+    switch (state->format) {
+    case XMPPIPE_FMT_CSV:
+      state->bufsz = 6144 + 1;
+      break;
+    default:
+      state->bufsz = 2048 + 1;
+      break;
+    }
+  }
+
   if (state->encode && BASE64_LENGTH(state->bufsz) + 1 > 0xffff) {
     usage(state);
     exit(2);
diff --git a/src/xmppipe.h b/src/xmppipe.h
index 9b1afce..bb4f95f 100644
--- a/src/xmppipe.h
+++ b/src/xmppipe.h
@@ -85,7 +85,7 @@ typedef struct {
       keepalive_fail; /* number of consecutive keepalives without a reply */
   u_int32_t keepalive_limit; /* number of keepalives without a reply */
   u_int32_t interval;        /* time since last keepalive (milliseconds) */
-  size_t bufsz;              /* size of read buffer */
+  ssize_t bufsz;             /* size of read buffer */
 
   int sm_enabled; /* stanzas: iq, message, presence */