diff --git a/arch/xtensa/src/esp32/esp32_cpustart.c b/arch/xtensa/src/esp32/esp32_cpustart.c
index d0f287c353..795263c736 100644
--- a/arch/xtensa/src/esp32/esp32_cpustart.c
+++ b/arch/xtensa/src/esp32/esp32_cpustart.c
@@ -55,9 +55,9 @@ static volatile spinlock_t g_appcpu_interlock SP_SECTION;
  * ROM function prototypes
  ****************************************************************************/
 
-void Cache_Flush(int cpu);
-void Cache_Read_Enable(int cpu);
-void ets_set_appcpu_boot_addr(uint32_t start);
+extern void Cache_Flush(int cpu);
+extern void Cache_Read_Enable(int cpu);
+extern void ets_set_appcpu_boot_addr(uint32_t start);
 
 /****************************************************************************
  * Private Functions
diff --git a/arch/xtensa/src/esp32/esp32_spiflash.c b/arch/xtensa/src/esp32/esp32_spiflash.c
index 58ead91be6..56197e6465 100644
--- a/arch/xtensa/src/esp32/esp32_spiflash.c
+++ b/arch/xtensa/src/esp32/esp32_spiflash.c
@@ -173,7 +173,7 @@ struct spiflash_cachestate_s
  * ROM function prototypes
  ****************************************************************************/
 
-void Cache_Flush(int cpu);
+extern void Cache_Flush(int cpu);
 
 /****************************************************************************
  * Private Functions Prototypes
diff --git a/arch/xtensa/src/esp32/rom/esp32_efuse.h b/arch/xtensa/src/esp32/rom/esp32_efuse.h
index c199624e04..3d2c61e3c6 100644
--- a/arch/xtensa/src/esp32/rom/esp32_efuse.h
+++ b/arch/xtensa/src/esp32/rom/esp32_efuse.h
@@ -33,32 +33,32 @@ extern "C"
 #endif
 
 /****************************************************************************
- * Public Function Prototypes
+ * ROM function prototypes
  ****************************************************************************/
 
 /****************************************************************************
  * Name: ets_efuse_read_op
  ****************************************************************************/
 
-void ets_efuse_read_op(void);
+extern void ets_efuse_read_op(void);
 
 /****************************************************************************
  * Name: ets_efuse_program_op
  ****************************************************************************/
 
-void ets_efuse_program_op(void);
+extern void ets_efuse_program_op(void);
 
 /****************************************************************************
  * Name: ets_efuse_get_8m_clock
  ****************************************************************************/
 
-uint32_t ets_efuse_get_8m_clock(void);
+extern uint32_t ets_efuse_get_8m_clock(void);
 
 /****************************************************************************
  * name: ets_efuse_get_spiconfig
  ****************************************************************************/
 
-uint32_t ets_efuse_get_spiconfig(void);
+extern uint32_t ets_efuse_get_spiconfig(void);
 
 #define EFUSE_SPICFG_SPI_DEFAULTS      0
 #define EFUSE_SPICFG_HSPI_DEFAULTS     1