diff --git a/src/dos/dos_execute.cpp b/src/dos/dos_execute.cpp
index d435d574..c7339972 100644
--- a/src/dos/dos_execute.cpp
+++ b/src/dos/dos_execute.cpp
@@ -232,8 +232,10 @@ bool DOS_Execute(char * name,PhysPt block_pt,Bit8u flags) {
 	if ((head.signature!=MAGIC1) && (head.signature!=MAGIC2)) iscom=true;
 	else {
 		headersize=head.headersize*16;
-		imagesize=(head.pages)*512-headersize; 
+		imagesize=(head.pages-1)*512-headersize; 
 		if (head.extrabytes) imagesize += head.extrabytes % 512;
+		// always load st least 512 Bytes (dos cache/dos bug?)
+		if (imagesize+headersize<512) imagesize = 512-headersize;
 	}
 	if (flags!=OVERLAY) {
 		/* Create an environment block */