diff --git a/c/src/exec/rtems/include/rtems.h b/c/src/exec/rtems/include/rtems.h
index 01c0b8478b..ddd7ca82d7 100644
--- a/c/src/exec/rtems/include/rtems.h
+++ b/c/src/exec/rtems/include/rtems.h
@@ -19,6 +19,8 @@
 #ifndef __RTEMS_RTEMS_GENERIC_h
 #define __RTEMS_RTEMS_GENERIC_h
 
+#define NO_IMPLICIT_EXTERN_C 1
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/cpukit/rtems/include/rtems.h b/cpukit/rtems/include/rtems.h
index 01c0b8478b..ddd7ca82d7 100644
--- a/cpukit/rtems/include/rtems.h
+++ b/cpukit/rtems/include/rtems.h
@@ -19,6 +19,8 @@
 #ifndef __RTEMS_RTEMS_GENERIC_h
 #define __RTEMS_RTEMS_GENERIC_h
 
+#define NO_IMPLICIT_EXTERN_C 1
+
 #ifdef __cplusplus
 extern "C" {
 #endif