diff --git a/src/hardware/vga_dac.cpp b/src/hardware/vga_dac.cpp
index ccad2290..fb3bce3b 100644
--- a/src/hardware/vga_dac.cpp
+++ b/src/hardware/vga_dac.cpp
@@ -96,6 +96,7 @@ static void write_p3c8(Bitu port,Bitu val,Bitu iolen) {
 	vga.dac.write_index=val;
 	vga.dac.pel_index=0;
 	vga.dac.state=DAC_WRITE;
+	vga.dac.read_index= val - 1;
 }
 
 static Bitu read_p3c8(Bitu port, Bitu iolen){