diff --git a/os/various/cpp_wrappers/ch.cpp b/os/various/cpp_wrappers/ch.cpp
index 54cf74692..2e3d05937 100644
--- a/os/various/cpp_wrappers/ch.cpp
+++ b/os/various/cpp_wrappers/ch.cpp
@@ -538,7 +538,7 @@ namespace chibios_rt {
 
   void Mutex::unlockS(void) {
 
-    chMtxLockS(&mutex);
+    chMtxUnlockS(&mutex);
   }
 
 #if CH_CFG_USE_CONDVARS