diff --git a/src/northbridge/intel/gm45/gm45.h b/src/northbridge/intel/gm45/gm45.h
index 34f734c..df9c449 100644
--- a/src/northbridge/intel/gm45/gm45.h
+++ b/src/northbridge/intel/gm45/gm45.h
@@ -433,6 +433,7 @@
 
 u32 decode_igd_memory_size(u32 gms);
 u32 decode_igd_gtt_size(u32 gsm);
+u32 decode_tseg_size(u8 esmramc);
 
 void init_iommu(void);