diff --git a/os/ports/RVCT/ARMCMx/chcore_v6m.c b/os/ports/RVCT/ARMCMx/chcore_v6m.c
index 6340df81c..db0cf7bf5 100644
--- a/os/ports/RVCT/ARMCMx/chcore_v6m.c
+++ b/os/ports/RVCT/ARMCMx/chcore_v6m.c
@@ -32,11 +32,6 @@
  */
 regarm_t _port_saved_pc;
 
-/**
- * @brief   IRQ nesting counter.
- */
-unsigned _port_irq_nesting;
-
 /**
  * @brief   System Timer vector.
  * @details This interrupt is used as system tick.