diff --git a/.travis.yml b/.travis.yml
index a9daa1f257..abade87365 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -52,6 +52,7 @@ jobs:
         # OSX has poor time resolution and the following tests do not have the correct output
         - (cd tests && ./run-tests --exclude 'uasyncio_(basic|heaplock|lock|wait_task)')
         # check for additional compiler errors/warnings
+        - make ${MAKEOPTS} -C ports/unix VARIANT=coverage submodules
         - make ${MAKEOPTS} -C ports/unix VARIANT=coverage
       after_failure:
         - tests/run-tests --print-failures
@@ -108,8 +109,8 @@ jobs:
         - python3 --version
       script:
         - make ${MAKEOPTS} -C mpy-cross
-        - make ${MAKEOPTS} -C ports/unix submodules
-        - make ${MAKEOPTS} -C ports/unix deplibs
+        - make ${MAKEOPTS} -C ports/unix VARIANT=coverage submodules
+        - make ${MAKEOPTS} -C ports/unix VARIANT=coverage deplibs
         - make ${MAKEOPTS} -C ports/unix VARIANT=coverage
         # run the main test suite
         - make -C ports/unix VARIANT=coverage test_full
@@ -143,8 +144,8 @@ jobs:
         - python3 --version
       script:
         - make ${MAKEOPTS} -C mpy-cross
-        - make ${MAKEOPTS} -C ports/unix MICROPY_FORCE_32BIT=1 submodules
-        - make ${MAKEOPTS} -C ports/unix MICROPY_FORCE_32BIT=1 deplibs
+        - make ${MAKEOPTS} -C ports/unix MICROPY_FORCE_32BIT=1 VARIANT=coverage submodules
+        - make ${MAKEOPTS} -C ports/unix MICROPY_FORCE_32BIT=1 VARIANT=coverage deplibs
         - make ${MAKEOPTS} -C ports/unix MICROPY_FORCE_32BIT=1 VARIANT=coverage
         # run the main test suite
         - make -C ports/unix MICROPY_FORCE_32BIT=1 VARIANT=coverage test_full || travis_terminate 1
@@ -183,8 +184,8 @@ jobs:
         - sudo apt-get install gcc-multilib libffi-dev:i386
       script:
         - make ${MAKEOPTS} -C mpy-cross PYTHON=python2
-        - make ${MAKEOPTS} -C ports/unix submodules
-        - make ${MAKEOPTS} -C ports/unix PYTHON=python2 deplibs
+        - make ${MAKEOPTS} -C ports/unix VARIANT=nanbox submodules
+        - make ${MAKEOPTS} -C ports/unix PYTHON=python2 VARIANT=nanbox deplibs
         - make ${MAKEOPTS} -C ports/unix PYTHON=python2 VARIANT=nanbox
         - make ${MAKEOPTS} -C ports/unix PYTHON=python2 VARIANT=nanbox test_full || travis_terminate 1
         - make ${MAKEOPTS} -C ports/unix clean
diff --git a/extmod/btstack/btstack.mk b/extmod/btstack/btstack.mk
index fe3a05272b..dd96e63379 100644
--- a/extmod/btstack/btstack.mk
+++ b/extmod/btstack/btstack.mk
@@ -14,6 +14,8 @@ CFLAGS_MOD += -DMICROPY_BLUETOOTH_BTSTACK=1
 
 BTSTACK_DIR = $(TOP)/lib/btstack
 
+ifneq ($(wildcard $(BTSTACK_DIR)/src),)
+
 include $(BTSTACK_DIR)/src/Makefile.inc
 include $(BTSTACK_DIR)/src/ble/Makefile.inc
 
@@ -52,3 +54,4 @@ endif
 $(BUILD)/lib/btstack/src/%.o: CFLAGS += $(BTSTACK_WARNING_CFLAGS)
 
 endif
+endif
diff --git a/ports/unix/Makefile b/ports/unix/Makefile
index 3e095a8d72..d9e77c26cd 100644
--- a/ports/unix/Makefile
+++ b/ports/unix/Makefile
@@ -31,7 +31,7 @@ UNAME_S := $(shell uname -s)
 # include py core make definitions
 include $(TOP)/py/py.mk
 
-GIT_SUBMODULES = lib/axtls lib/berkeley-db-1.xx lib/libffi
+GIT_SUBMODULES += lib/axtls lib/berkeley-db-1.xx lib/libffi
 
 INC +=  -I.
 INC +=  -I$(TOP)
@@ -146,6 +146,8 @@ MICROPY_BLUETOOTH_BTSTACK ?= 1
 MICROPY_BLUETOOTH_BTSTACK_USB ?= 1
 
 ifeq ($(MICROPY_BLUETOOTH_BTSTACK),1)
+GIT_SUBMODULES += lib/btstack
+
 include $(TOP)/extmod/btstack/btstack.mk
 endif