diff --git a/libraries/AP_HAL_ChibiOS/Device.cpp b/libraries/AP_HAL_ChibiOS/Device.cpp
index 7e8f5f8d43..4c51a5efe9 100644
--- a/libraries/AP_HAL_ChibiOS/Device.cpp
+++ b/libraries/AP_HAL_ChibiOS/Device.cpp
@@ -89,6 +89,7 @@ void DeviceBus::bus_thread(void *arg)
     return;
 }
 
+#if CH_CFG_USE_HEAP == TRUE
 AP_HAL::Device::PeriodicHandle DeviceBus::register_periodic_callback(uint32_t period_usec, AP_HAL::Device::PeriodicCb cb, AP_HAL::Device *_hal_device)
 {
     if (!thread_started) {
@@ -133,6 +134,7 @@ AP_HAL::Device::PeriodicHandle DeviceBus::register_periodic_callback(uint32_t pe
 
     return callback;
 }
+#endif // CH_CFG_USE_HEAP
 
 /*
  * Adjust the timer for the next call: it needs to be called from the bus
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/malloc.c b/libraries/AP_HAL_ChibiOS/hwdef/common/malloc.c
index cb11620198..626c510ef1 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/malloc.c
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/malloc.c
@@ -31,6 +31,8 @@
 #include <stdarg.h>
 #include "stm32_util.h"
 
+#if CH_CFG_USE_HEAP == TRUE
+
 #define MIN_ALIGNMENT 8
 
 #if defined(CCM_RAM_SIZE_KB)
@@ -161,3 +163,5 @@ size_t mem_available(void)
     
     return totalp;
 }
+
+#endif // CH_CFG_USE_HEAP
diff --git a/libraries/AP_HAL_ChibiOS/shared_dma.cpp b/libraries/AP_HAL_ChibiOS/shared_dma.cpp
index 59669a0755..e51a9a2676 100644
--- a/libraries/AP_HAL_ChibiOS/shared_dma.cpp
+++ b/libraries/AP_HAL_ChibiOS/shared_dma.cpp
@@ -20,6 +20,8 @@
   code to handle sharing of DMA channels between peripherals
  */
 
+#if CH_CFG_USE_SEMAPHORES == TRUE
+
 using namespace ChibiOS;
 
 Shared_DMA::dma_lock Shared_DMA::locks[SHARED_DMA_MAX_STREAM_ID];
@@ -183,3 +185,5 @@ void Shared_DMA::lock_all(void)
         chBSemWait(&locks[i].semaphore);
     }
 }
+
+#endif // CH_CFG_USE_SEMAPHORES
diff --git a/libraries/AP_HAL_ChibiOS/shared_dma.h b/libraries/AP_HAL_ChibiOS/shared_dma.h
index 59f42ea8d7..6f1b72171e 100644
--- a/libraries/AP_HAL_ChibiOS/shared_dma.h
+++ b/libraries/AP_HAL_ChibiOS/shared_dma.h
@@ -81,7 +81,9 @@ private:
     
     static struct dma_lock {
         // semaphore to ensure only one peripheral uses a DMA channel at a time
+#if CH_CFG_USE_SEMAPHORES == TRUE
         binary_semaphore_t semaphore;
+#endif // CH_CFG_USE_SEMAPHORES
 
         // a de-allocation function that is called to release an existing user
         dma_deallocate_fn_t deallocate;
@@ -90,3 +92,4 @@ private:
         Shared_DMA *obj;
     } locks[SHARED_DMA_MAX_STREAM_ID];
 };
+