diff --git a/arch/arm/src/efm32/Make.defs b/arch/arm/src/efm32/Make.defs
index d60d47b8208..8492cec0728 100644
--- a/arch/arm/src/efm32/Make.defs
+++ b/arch/arm/src/efm32/Make.defs
@@ -94,7 +94,8 @@ ifeq ($(CONFIG_ARMV7M_CMNVECTOR),y)
 CHIP_ASRCS += efm32_vectors.S
 endif
 
-CHIP_CSRCS = efm32_start.c efm32_clockconfig.c efm32_irq.c efm32_timerisr.c
+CHIP_CSRCS  = efm32_start.c efm32_clockconfig.c efm32_irq.c efm32_timerisr.c
+CHIP_CSRCS += efm32_lowputc.c
 
 ifneq ($(CONFIG_ARCH_IDLE_CUSTOM),y)
 CHIP_CSRCS += efm32_idle.c