diff --git a/openmp/libomptarget/DeviceRTL/include/Mapping.h b/openmp/libomptarget/DeviceRTL/include/Mapping.h
index c9e07bab3c9a7..6bf7e0006c3c6 100644
--- a/openmp/libomptarget/DeviceRTL/include/Mapping.h
+++ b/openmp/libomptarget/DeviceRTL/include/Mapping.h
@@ -51,6 +51,8 @@ bool isInitialThreadInLevel0(bool IsSPMD);
 /// in the warp.
 bool isLeaderInWarp();
 
+bool isMainThreadInBlock();
+
 /// Return a mask describing all active threads in the warp.
 LaneMaskTy activemask();