diff --git a/libraries/AP_HAL/Storage.h b/libraries/AP_HAL/Storage.h
index e3b570511a..e4edb7a0b9 100644
--- a/libraries/AP_HAL/Storage.h
+++ b/libraries/AP_HAL/Storage.h
@@ -16,7 +16,7 @@ public:
     virtual void write_byte(uint16_t loc, uint8_t value) = 0;
     virtual void write_word(uint16_t loc, uint16_t value) = 0;
     virtual void write_dword(uint16_t loc, uint32_t value) = 0;
-    virtual void write_block(uint16_t dst, void* src, size_t n) = 0;
+    virtual void write_block(uint16_t dst, const void* src, size_t n) = 0;
 };
 
 #endif // __AP_HAL_STORAGE_H__
diff --git a/libraries/AP_HAL_AVR/Storage.cpp b/libraries/AP_HAL_AVR/Storage.cpp
index 1670c4ff8b..518a24a7e3 100644
--- a/libraries/AP_HAL_AVR/Storage.cpp
+++ b/libraries/AP_HAL_AVR/Storage.cpp
@@ -37,7 +37,7 @@ void AVREEPROMStorage::write_dword(uint16_t loc, uint32_t value) {
     write_block(loc, &value, sizeof(value));
 }
 
-void AVREEPROMStorage::write_block(uint16_t dst, void *src, size_t n) {
+void AVREEPROMStorage::write_block(uint16_t dst, const void *src, size_t n) {
     uint8_t *p = (uint8_t *)src;
     while (n--) {
         write_byte(dst++, *p++);
diff --git a/libraries/AP_HAL_AVR/Storage.h b/libraries/AP_HAL_AVR/Storage.h
index fc70fa964e..e102baaec5 100644
--- a/libraries/AP_HAL_AVR/Storage.h
+++ b/libraries/AP_HAL_AVR/Storage.h
@@ -18,7 +18,7 @@ public:
     void write_byte(uint16_t loc, uint8_t value);
     void write_word(uint16_t loc, uint16_t value);
     void write_dword(uint16_t loc, uint32_t value);
-    void write_block(uint16_t dst, void* src, size_t n);
+    void write_block(uint16_t dst, const void* src, size_t n);
 };
 
 #endif // __AP_HAL_AVR_STORAGE_H__
diff --git a/libraries/AP_HAL_AVR_SITL/Storage.cpp b/libraries/AP_HAL_AVR_SITL/Storage.cpp
index 62d995174f..17bbb74d59 100644
--- a/libraries/AP_HAL_AVR_SITL/Storage.cpp
+++ b/libraries/AP_HAL_AVR_SITL/Storage.cpp
@@ -73,7 +73,7 @@ void SITLEEPROMStorage::write_dword(uint16_t loc, uint32_t value)
 	assert(pwrite(_eeprom_fd, &value, 4, loc) == 4);
 }
 
-void SITLEEPROMStorage::write_block(uint16_t dst, void *src, size_t n) 
+void SITLEEPROMStorage::write_block(uint16_t dst, const void *src, size_t n) 
 {
 	assert(dst < 4096);
 	_eeprom_open();
diff --git a/libraries/AP_HAL_AVR_SITL/Storage.h b/libraries/AP_HAL_AVR_SITL/Storage.h
index 863d6cbcb9..5e105774bb 100644
--- a/libraries/AP_HAL_AVR_SITL/Storage.h
+++ b/libraries/AP_HAL_AVR_SITL/Storage.h
@@ -20,7 +20,7 @@ public:
     void write_byte(uint16_t loc, uint8_t value);
     void write_word(uint16_t loc, uint16_t value);
     void write_dword(uint16_t loc, uint32_t value);
-    void write_block(uint16_t dst, void* src, size_t n);
+    void write_block(uint16_t dst, const void* src, size_t n);
 
 private:
     int _eeprom_fd;
diff --git a/libraries/AP_HAL_Empty/Storage.cpp b/libraries/AP_HAL_Empty/Storage.cpp
index 3c8baaf5b2..4762eadbda 100644
--- a/libraries/AP_HAL_Empty/Storage.cpp
+++ b/libraries/AP_HAL_Empty/Storage.cpp
@@ -35,6 +35,6 @@ void EmptyStorage::write_word(uint16_t loc, uint16_t value)
 void EmptyStorage::write_dword(uint16_t loc, uint32_t value)
 {}
 
-void EmptyStorage::write_block(uint16_t loc, void* src, size_t n)
+void EmptyStorage::write_block(uint16_t loc, const void* src, size_t n)
 {}
 
diff --git a/libraries/AP_HAL_Empty/Storage.h b/libraries/AP_HAL_Empty/Storage.h
index b536d2cf48..777a2d3518 100644
--- a/libraries/AP_HAL_Empty/Storage.h
+++ b/libraries/AP_HAL_Empty/Storage.h
@@ -16,7 +16,7 @@ public:
     void write_byte(uint16_t loc, uint8_t value);
     void write_word(uint16_t loc, uint16_t value);
     void write_dword(uint16_t loc, uint32_t value);
-    void write_block(uint16_t dst, void* src, size_t n);
+    void write_block(uint16_t dst, const void* src, size_t n);
 };
 
 #endif // __AP_HAL_EMPTY_STORAGE_H__
diff --git a/libraries/AP_HAL_PX4/Storage.cpp b/libraries/AP_HAL_PX4/Storage.cpp
index a6a44f1506..0f1ad33e3e 100644
--- a/libraries/AP_HAL_PX4/Storage.cpp
+++ b/libraries/AP_HAL_PX4/Storage.cpp
@@ -165,7 +165,7 @@ void PX4Storage::write_dword(uint16_t loc, uint32_t value)
 	}
 }
 
-void PX4Storage::write_block(uint16_t loc, void *src, size_t n) 
+void PX4Storage::write_block(uint16_t loc, const void *src, size_t n) 
 {
 	if (loc >= sizeof(_buffer)-(n-1)) {
 		return;
diff --git a/libraries/AP_HAL_PX4/Storage.h b/libraries/AP_HAL_PX4/Storage.h
index eb28da8f0e..1bd4ece16e 100644
--- a/libraries/AP_HAL_PX4/Storage.h
+++ b/libraries/AP_HAL_PX4/Storage.h
@@ -30,7 +30,7 @@ public:
     void write_byte(uint16_t loc, uint8_t value);
     void write_word(uint16_t loc, uint16_t value);
     void write_dword(uint16_t loc, uint32_t value);
-    void write_block(uint16_t dst, void* src, size_t n);
+    void write_block(uint16_t dst, const void* src, size_t n);
 
     void _timer_tick(void);
 
diff --git a/libraries/AP_HAL_SMACCM/Storage.cpp b/libraries/AP_HAL_SMACCM/Storage.cpp
index 9256ae2789..515911e463 100644
--- a/libraries/AP_HAL_SMACCM/Storage.cpp
+++ b/libraries/AP_HAL_SMACCM/Storage.cpp
@@ -78,7 +78,7 @@ void SMACCMStorage::write_dword(uint16_t loc, uint32_t value)
   eeprom_write(loc, (uint8_t*)&value, sizeof(value));
 }
 
-void SMACCMStorage::write_block(uint16_t loc, void* src, size_t n)
+void SMACCMStorage::write_block(uint16_t loc, const void* src, size_t n)
 {
   eeprom_write(loc, (const uint8_t *)src, n);
 }
diff --git a/libraries/AP_HAL_SMACCM/Storage.h b/libraries/AP_HAL_SMACCM/Storage.h
index 5d614911b5..ac3946c494 100644
--- a/libraries/AP_HAL_SMACCM/Storage.h
+++ b/libraries/AP_HAL_SMACCM/Storage.h
@@ -29,7 +29,7 @@ public:
   void write_byte(uint16_t loc, uint8_t value);
   void write_word(uint16_t loc, uint16_t value);
   void write_dword(uint16_t loc, uint32_t value);
-  void write_block(uint16_t dst, void* src, size_t n);
+  void write_block(uint16_t dst, const void* src, size_t n);
 };
 
 #endif // __AP_HAL_SMACCM_STORAGE_H__