diff --git a/libraries/AP_HAL/AnalogIn.h b/libraries/AP_HAL/AnalogIn.h
index ca18c0a926..279c300c3c 100644
--- a/libraries/AP_HAL/AnalogIn.h
+++ b/libraries/AP_HAL/AnalogIn.h
@@ -41,8 +41,7 @@ public:
 
 class AP_HAL::AnalogIn {
 public:
-    virtual void init(void* implspecific) { }
-    virtual void init() { }
+    virtual void init() = 0;
     virtual AP_HAL::AnalogSource* channel(int16_t n) = 0;
 
     // board 5V rail voltage in volts
diff --git a/libraries/AP_HAL/RCInput.h b/libraries/AP_HAL/RCInput.h
index 41bd87ecb8..9336a26a4a 100644
--- a/libraries/AP_HAL/RCInput.h
+++ b/libraries/AP_HAL/RCInput.h
@@ -15,8 +15,7 @@ public:
      * known to the programmer. (Its too difficult to describe this dependency
      * in the C++ type system.)
      */
-    virtual void init(void* implspecific) { }
-    virtual void init() { }
+    virtual void init() = 0;
     virtual void deinit() {};
 
     /**
diff --git a/libraries/AP_HAL/RCOutput.h b/libraries/AP_HAL/RCOutput.h
index db6eb7630b..17c091d2f3 100644
--- a/libraries/AP_HAL/RCOutput.h
+++ b/libraries/AP_HAL/RCOutput.h
@@ -32,8 +32,7 @@
 
 class AP_HAL::RCOutput {
 public:
-    virtual void init(void* implspecific) { }
-    virtual void init() { }
+    virtual void init() = 0;
 
     /* Output freq (1/period) control */
     virtual void     set_freq(uint32_t chmask, uint16_t freq_hz) = 0;
diff --git a/libraries/AP_HAL/SPIDriver.h b/libraries/AP_HAL/SPIDriver.h
index 415e218296..f1496e95c2 100644
--- a/libraries/AP_HAL/SPIDriver.h
+++ b/libraries/AP_HAL/SPIDriver.h
@@ -7,8 +7,7 @@
 
 class AP_HAL::SPIDeviceManager {
 public:
-    virtual void init(void *) { }
-    virtual void init() { }
+    virtual void init() = 0;
     virtual AP_HAL::SPIDeviceDriver* device(enum AP_HAL::SPIDevice, uint8_t index = 0) = 0;
 };
 
diff --git a/libraries/AP_HAL/Scheduler.h b/libraries/AP_HAL/Scheduler.h
index 7f0c804999..cfb2c0d05a 100644
--- a/libraries/AP_HAL/Scheduler.h
+++ b/libraries/AP_HAL/Scheduler.h
@@ -13,8 +13,7 @@
 class AP_HAL::Scheduler {
 public:
     Scheduler() {}
-    virtual void     init(void* implspecific) { }
-    virtual void     init() { }
+    virtual void     init() = 0;
     virtual void     delay(uint16_t ms) = 0;
 
     /*
diff --git a/libraries/AP_HAL/Storage.h b/libraries/AP_HAL/Storage.h
index d55e14cd14..4a1b4b5338 100644
--- a/libraries/AP_HAL/Storage.h
+++ b/libraries/AP_HAL/Storage.h
@@ -7,8 +7,7 @@
 
 class AP_HAL::Storage {
 public:
-    virtual void init(void *) { }
-    virtual void init() { }
+    virtual void init() = 0;
     virtual void read_block(void *dst, uint16_t src, size_t n) = 0;
     virtual void write_block(uint16_t dst, const void* src, size_t n) = 0;
 };