diff --git a/lib_xua/module_build_info b/lib_xua/module_build_info
index ae82693c..7d9f5ddd 100644
--- a/lib_xua/module_build_info
+++ b/lib_xua/module_build_info
@@ -1,5 +1,13 @@
 VERSION = 3.2.0
 
+DEBUG ?= 0
+
+ifeq ($(DEBUG),1)
+DEBUG_FLAGS = -g -DXASSERT_ENABLE_ASSERTIONS_DECOUPLE=1
+else
+DEBUG_FLAGS = -DXASSERT_DISABLE_ASSERTIONS_DECOUPLE=1
+endif
+
 DEPENDENT_MODULES = lib_locks(>=2.1.0) \
                     lib_logging(>=3.1.1) \
                     lib_mic_array(>=4.5.0) \
@@ -11,7 +19,8 @@ MODULE_XCC_FLAGS = $(XCC_FLAGS) \
                    -O3 \
                    -DREF_CLK_FREQ=100 \
                    -fasm-linenum \
-                   -fcomment-asm
+                   -fcomment-asm \
+                    $(DEBUG_FLAGS)
 
 # Core
 XCC_FLAGS_xua_endpoint0.c = $(MODULE_XCC_FLAGS) -Os -mno-dual-issue
diff --git a/lib_xua/src/core/buffer/decouple/decouple.xc b/lib_xua/src/core/buffer/decouple/decouple.xc
index 085d27cf..4a4bcba5 100644
--- a/lib_xua/src/core/buffer/decouple/decouple.xc
+++ b/lib_xua/src/core/buffer/decouple/decouple.xc
@@ -2,6 +2,9 @@
 // This Software is subject to the terms of the XMOS Public Licence: Version 1.
 #include "xua.h"
 
+#define XASSERT_UNIT DECOUPLE
+#include "xassert.h"
+
 #if XUA_USB_EN
 #include <xs1.h>
 #include "xc_ptr.h"
@@ -149,6 +152,7 @@ void handle_audio_request(chanend c_mix_out)
 {
     int space_left;
 #if(defined XUA_USB_DESCRIPTOR_OVERWRITE_RATE_RES)
+    #error
     g_curSubSlot_Out = get_usb_to_device_bit_res() >> 3;
     g_curSubSlot_In = get_device_to_usb_bit_res() >> 3;
 #endif
@@ -502,16 +506,18 @@ __builtin_unreachable();
                 space_left = aud_to_host_fifo_end - g_aud_to_host_wrptr;
             }
 
-            if((space_left < (totalSampsToWrite * g_numUsbChan_In * g_curSubSlot_In + 4)))
+            assert(space_left > 0 && msg("space_left expected to be positive"));
+
+            if((space_left < (totalSampsToWrite * g_numUsbChan_In * (unsigned) g_curSubSlot_In + 4)))
             {
                 /* In pipe has filled its buffer - we need to overflow
                  * Accept the packet, and throw away the oldest in the buffer */
 
-                int sampFreq;
+                unsigned sampFreq;
                 GET_SHARED_GLOBAL(sampFreq, g_freqChange_sampFreq);
                 int min, mid, max;
                 GetADCCounts(sampFreq, min, mid, max);
-                int max_pkt_size = ((max * g_curSubSlot_In * g_numUsbChan_In + 3) & ~0x3) + 4;
+                const int max_pkt_size = ((max * g_curSubSlot_In * g_numUsbChan_In + 3) & ~0x3) + 4;
 
                 /* Keep throwing away packets until buffer contains two packets */
                 do
@@ -537,6 +543,8 @@ __builtin_unreachable();
                     space_left += datalength;
                     SET_SHARED_GLOBAL(g_aud_to_host_rdptr, rdPtr);
 
+                    assert(rdPtr < aud_to_host_fifo_end && msg("rdPtr must be within buffer"));
+
                 } while(space_left < (BUFF_SIZE_IN - 2 * max_pkt_size));
             }
 
diff --git a/lib_xua/src/core/endpoint0/xua_endpoint0.c b/lib_xua/src/core/endpoint0/xua_endpoint0.c
index 0ef1ff6b..d69fb57e 100755
--- a/lib_xua/src/core/endpoint0/xua_endpoint0.c
+++ b/lib_xua/src/core/endpoint0/xua_endpoint0.c
@@ -130,7 +130,11 @@ unsigned g_curStreamAlt_Out = 0;
 unsigned g_curStreamAlt_In = 0;
 
 /* Global variable for current USB bus speed (i.e. FS/HS) */
-XUD_BusSpeed_t g_curUsbSpeed = 0;
+#if (AUDIO_CLASS == 2)
+XUD_BusSpeed_t g_curUsbSpeed = XUD_SPEED_HS;
+#else
+XUD_BusSpeed_t g_curUsbSpeed = XUD_SPEED_FS;
+#endif
 
 /* Global variables for current USB Vendor and Product strings */
 char g_vendor_str[XUA_MAX_STR_LEN] = VENDOR_STR;