diff --git a/core/include/kernel.h b/core/include/kernel.h
index 018549bbf0..221213eec4 100644
--- a/core/include/kernel.h
+++ b/core/include/kernel.h
@@ -67,12 +67,6 @@
 #endif
 
 /* ------------------------------------------------------------------------- */
-/**
- * @def PID_NULL
- * @brief Identifier to detect an invalid PID
- */
-#define KERNEL_PID_NULL -1
-
 /**
  * @def PRIORITY_MIN
  * @brief Least priority a thread can have
diff --git a/core/include/kernel_types.h b/core/include/kernel_types.h
index 15e07cf871..04c026e9db 100644
--- a/core/include/kernel_types.h
+++ b/core/include/kernel_types.h
@@ -4,6 +4,12 @@
 #include <stdint.h>
 #include <inttypes.h>
 
+/**
+ * @def KERNEL_PID_NULL
+ * @brief Identifier to detect an invalid PID
+ */
+#define KERNEL_PID_NULL -1
+
 /**
  * Macro for printing formatter
  */