diff --git a/examples/natmod/btree/Makefile b/examples/natmod/btree/Makefile
index 6273ccc657..bcaa7a93d1 100644
--- a/examples/natmod/btree/Makefile
+++ b/examples/natmod/btree/Makefile
@@ -36,6 +36,9 @@ ifeq ($(ARCH),xtensa)
 MPY_EXTERN_SYM_FILE=$(MPY_DIR)/ports/esp8266/boards/eagle.rom.addr.v6.ld
 endif
 
+# Use our own errno implementation if Picolibc is used
+CFLAGS += -D__PICOLIBC_ERRNO_FUNCTION=__errno
+
 include $(MPY_DIR)/py/dynruntime.mk
 
 # btree needs gnu99 defined
diff --git a/ports/qemu/Makefile b/ports/qemu/Makefile
index e9e1e0f957..646659ceda 100644
--- a/ports/qemu/Makefile
+++ b/ports/qemu/Makefile
@@ -191,12 +191,11 @@ test_full: $(BUILD)/firmware.elf
 	cd $(TOP)/tests && ./run-tests.py $(RUN_TESTS_FULL_ARGS) --via-mpy
 	cd $(TOP)/tests && ./run-tests.py $(RUN_TESTS_FULL_ARGS) --via-mpy --emit native
 
-# "btree" currently does not build for rv32imc (Picolibc TLS incompatibility).
 .PHONY: test_natmod
 test_natmod: $(BUILD)/firmware.elf
 	$(eval DIRNAME=ports/$(notdir $(CURDIR)))
 	cd $(TOP)/tests && \
-		for natmod in deflate framebuf heapq random_basic re; do \
+		for natmod in btree deflate framebuf heapq random_basic re; do \
 		./run-natmodtests.py -p -d execpty:"$(QEMU_SYSTEM) $(QEMU_ARGS) -serial pty -kernel ../$(DIRNAME)/$<" extmod/$$natmod*.py; \
 		done
 
diff --git a/tools/ci.sh b/tools/ci.sh
index 564b7810f5..510bb3a4d3 100755
--- a/tools/ci.sh
+++ b/tools/ci.sh
@@ -563,7 +563,7 @@ function ci_native_mpy_modules_build {
     else
         arch=$1
     fi
-    for natmod in deflate features1 features3 features4 framebuf heapq random re
+    for natmod in btree deflate features1 features3 features4 framebuf heapq random re
     do
         make -C examples/natmod/$natmod ARCH=$arch clean
         make -C examples/natmod/$natmod ARCH=$arch
@@ -576,12 +576,6 @@ function ci_native_mpy_modules_build {
     else
         make -C examples/natmod/features2 ARCH=$arch
     fi
-
-    # btree requires thread local storage support on rv32imc.
-    if [ $arch != "rv32imc" ]; then
-        make -C examples/natmod/btree ARCH=$arch clean
-        make -C examples/natmod/btree ARCH=$arch
-    fi
 }
 
 function ci_native_mpy_modules_32bit_build {