diff --git a/build/jam/images/AnybootImage b/build/jam/images/AnybootImage
old mode 100644
new mode 100755
index d926f3cace..0c44c1f625
--- a/build/jam/images/AnybootImage
+++ b/build/jam/images/AnybootImage
@@ -33,7 +33,7 @@ actions BuildAnybootImage1 {
 }
 
 local baseMBR = base_mbr.bin ;
-local mbrSource = [ FDirName $(HAIKU_TOP) src bin writembr mbr.S ] ;
+local mbrSource = [ FDirName $(HAIKU_TOP) src bin writembr mbr.nasm ] ;
 BuildAnybootMBR $(baseMBR) : $(mbrSource) ;
 MakeLocate $(baseMBR) : $(HAIKU_OUTPUT_DIR) ;
 MakeLocate $(HAIKU_ANYBOOT) : $(HAIKU_ANYBOOT_DIR) ;
diff --git a/src/bin/writembr/Jamfile b/src/bin/writembr/Jamfile
index 6c33228b4f..2674876573 100755
--- a/src/bin/writembr/Jamfile
+++ b/src/bin/writembr/Jamfile
@@ -10,7 +10,7 @@ Application writembr :
 
 # Assemble the MBR code, and convert it into a header file
 
-NASMFLAGS on [ FGristFiles mbr.bin ] = -f bin -O5 ;
+NASMFLAGS on [ FGristFiles mbr.bin ] = -f bin -O5 -dMBR_CODE_ONLY=1 ;
 
 Object [ FGristFiles mbr.bin ] : mbr.nasm ;