diff --git a/src/modules/px4iofirmware/mixer.cpp b/src/modules/px4iofirmware/mixer.cpp
index 4ff95bd5af..bbcd39c69f 100644
--- a/src/modules/px4iofirmware/mixer.cpp
+++ b/src/modules/px4iofirmware/mixer.cpp
@@ -418,7 +418,7 @@ mixer_callback(uintptr_t handle,
  * not loaded faithfully.
  */
 
-static char mixer_text[256];		/* large enough for one mixer */
+static char mixer_text[200];		/* large enough for one mixer */
 static unsigned mixer_text_length = 0;
 
 int
diff --git a/src/modules/px4iofirmware/px4io.c b/src/modules/px4iofirmware/px4io.c
index 1ee50d5a7f..4715cfd063 100644
--- a/src/modules/px4iofirmware/px4io.c
+++ b/src/modules/px4iofirmware/px4io.c
@@ -82,7 +82,7 @@ static volatile uint8_t msg_next_out, msg_next_in;
  * for mixer handling. Do not allocate more than 80 bytes for
  * output.
  */
-#define NUM_MSG 2
+#define NUM_MSG 1
 static char msg[NUM_MSG][40];
 
 static void heartbeat_blink(void);