diff --git a/RSSIRB.h b/RSSIRB.h
index 0f855a3..f3db3de 100644
--- a/RSSIRB.h
+++ b/RSSIRB.h
@@ -23,10 +23,8 @@ Boston, MA  02110-1301, USA.
 
 #if defined(STM32F4XX)
 #include "stm32f4xx.h"
-#include <cstddef>
 #elif defined(STM32F7XX)
 #include "stm32f7xx.h"
-#include <cstddef>
 #elif defined(STM32F105xC)
 #include "stm32f1xx.h"
 #include <cstddef>
diff --git a/SampleRB.h b/SampleRB.h
index 305bf8b..e0b6269 100644
--- a/SampleRB.h
+++ b/SampleRB.h
@@ -23,10 +23,8 @@ Boston, MA  02110-1301, USA.
 
 #if defined(STM32F4XX)
 #include "stm32f4xx.h"
-#include <cstddef>
 #elif defined(STM32F7XX)
 #include "stm32f7xx.h"
-#include <cstddef>
 #elif defined(STM32F105xC)
 #include "stm32f1xx.h"
 #include <cstddef>
diff --git a/SerialRB.h b/SerialRB.h
index 91ebcc1..7b6b7b9 100644
--- a/SerialRB.h
+++ b/SerialRB.h
@@ -23,10 +23,8 @@ Boston, MA  02110-1301, USA.
 
 #if defined(STM32F4XX)
 #include "stm32f4xx.h"
-#include <cstddef>
 #elif defined(STM32F7XX)
 #include "stm32f7xx.h"
-#include <cstddef>
 #elif defined(STM32F105xC)
 #include "stm32f1xx.h"
 #include <cstddef>
diff --git a/Utils.h b/Utils.h
index 7656b23..95cb1d5 100644
--- a/Utils.h
+++ b/Utils.h
@@ -21,10 +21,8 @@
 
 #if defined(STM32F4XX)
 #include "stm32f4xx.h"
-#include <cstddef>
 #elif defined(STM32F7XX)
 #include "stm32f7xx.h"
-#include <cstddef>
 #elif defined(STM32F105xC)
 #include "stm32f1xx.h"
 #include <cstddef>