diff --git a/VAX/vax780_vmb_exe.h b/VAX/vax780_vmb_exe.h
index e15fe616..6b6af820 100644
--- a/VAX/vax780_vmb_exe.h
+++ b/VAX/vax780_vmb_exe.h
@@ -1,7 +1,9 @@
+#ifndef ROM_vax780_vmb_exe_H
+#define ROM_vax780_vmb_exe_H 0
 /*
-   VAX/vax780_vmb_exe.h         produced at Tue Sep 20 04:39:17 2011
-   from VAX/vmb.exe which was last modified at Tue Sep 20 03:24:44 2011
-   file size: 44544 (0xAE00)
+   VAX/vax780_vmb_exe.h         produced at Sun Feb 26 12:32:44 2012
+   from VAX/vmb.exe which was last modified at Sat Feb 18 00:01:12 2012
+   file size: 44544 (0xAE00) - checksum: 0xFFC014CC
 */
 unsigned char vax780_vmb_exe[] = {
 0xD4,0xEF,0x34,0x61,0x00,0x00,0x17,0xEF,0xB8,0x5D,0x00,0x00,0xC1,0xAB,0x38,0xAB,
@@ -2788,3 +2790,4 @@ unsigned char vax780_vmb_exe[] = {
 0x4C,0x52,0x45,0x41,0x44,0x3A,0x58,0x2D,0x32,0x20,0x20,0x43,0x4F,0x4E,0x49,0x4F,
 0x3A,0x58,0x2D,0x33,0x20,0x20,0x2A,0x45,0x6E,0x64,0x20,0x6F,0x66,0x20,0x49,0x64,
 0x65,0x6E,0x74,0x20,0x6C,0x69,0x73,0x74,0x73,0x2A,0x00,0x00,0x00,0x00,0x00,0x00,};
+#endif /* ROM_vax780_vmb_exe_H */
diff --git a/VAX/vax_ka655x_bin.h b/VAX/vax_ka655x_bin.h
index 7fdea0c6..6cc64347 100644
--- a/VAX/vax_ka655x_bin.h
+++ b/VAX/vax_ka655x_bin.h
@@ -1,7 +1,9 @@
+#ifndef ROM_vax_ka655x_bin_H
+#define ROM_vax_ka655x_bin_H 0
 /*
-   VAX/vax_ka655x_bin.h         produced at Tue Sep 20 04:39:07 2011
-   from VAX/ka655x.bin which was last modified at Tue Sep 20 03:24:43 2011
-   file size: 131072 (0x20000)
+   VAX/vax_ka655x_bin.h         produced at Sun Feb 26 12:32:44 2012
+   from VAX/ka655x.bin which was last modified at Sat Feb 18 00:01:12 2012
+   file size: 131072 (0x20000) - checksum: 0xFF7673B6
 */
 unsigned char vax_ka655x_bin[] = {
 0x11,0x22,0x11,0xFE,0x02,0x03,0x53,0x01,0x31,0x89,0x03,0x00,0x31,0x8B,0x03,0x00,
@@ -8196,3 +8198,4 @@ unsigned char vax_ka655x_bin[] = {
 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,};
+#endif /* ROM_vax_ka655x_bin_H */
diff --git a/sim_BuildROMs.c b/sim_BuildROMs.c
index 3a60e248..ba573de3 100644
--- a/sim_BuildROMs.c
+++ b/sim_BuildROMs.c
@@ -55,6 +55,7 @@
 
 int sim_make_ROM_include(const char *rom_filename,
                          int expected_size,
+                         int expected_checksum,
                          const char *include_filename, 
                          const char *rom_array_name)
 {
@@ -65,6 +66,7 @@ int bytes_written = 0;
 int c;
 struct stat statb;
 unsigned char *ROMData = NULL;
+unsigned int checksum = 0;
 
 if (NULL == (rFile = fopen (rom_filename, "rb"))) {
     printf ("Error Opening '%s' for input: %s\n", rom_filename, strerror(errno));
@@ -76,7 +78,7 @@ if (stat (rom_filename, &statb)) {
     return -1;
     }
 if (statb.st_size != expected_size) {
-    printf ("Error: ROM file '%s' has an unexpected size: %d vs %d\n", (int)statb.st_size, expected_size);
+    printf ("Error: ROM file '%s' has an unexpected size: %d vs %d\n", rom_filename, (int)statb.st_size, expected_size);
     printf ("This can happen if the file was transferred or unpacked incorrectly\n");
     printf ("and in the process tried to convert line endings rather than passing\n");
     printf ("the file's contents unmodified\n");
@@ -91,6 +93,17 @@ if (statb.st_size != fread (ROMData, sizeof(*ROMData), statb.st_size, rFile)) {
     return -1;
     }
 fclose (rFile);
+for (c=0; c<statb.st_size; ++c)
+    checksum += ROMData[c];
+checksum = ~checksum;
+if ((expected_checksum != 0) && (checksum != expected_checksum)) {
+    printf ("Error: ROM file '%s' has an unexpected checksum: 0x%08X vs 0x%08X\n", rom_filename, checksum, expected_checksum);
+    printf ("This can happen if the file was transferred or unpacked incorrectly\n");
+    printf ("and in the process tried to convert line endings rather than passing\n");
+    printf ("the file's contents unmodified\n");
+    fclose (rFile);
+    return -1;
+    }
 /*
  * If the target include file already exists, determine if it contains the exact
  * data in the base ROM image.  If so, then we are already done
@@ -139,7 +152,7 @@ fprintf (iFile, "#define ROM_%s_H 0\n", rom_array_name);
 fprintf (iFile, "/*\n");
 fprintf (iFile, "   %s         produced at %s", include_filename, ctime(&now));
 fprintf (iFile, "   from %s which was last modified at %s", rom_filename, ctime(&statb.st_mtime));
-fprintf (iFile, "   file size: %d (0x%X)\n", (int)statb.st_size, (int)statb.st_size);
+fprintf (iFile, "   file size: %d (0x%X) - checksum: 0x%08X\n", (int)statb.st_size, (int)statb.st_size, checksum);
 fprintf (iFile, "*/\n");
 fprintf (iFile, "unsigned char %s[] = {", rom_array_name);
 for (bytes_written=0;bytes_written<statb.st_size; ++bytes_written) {
@@ -165,7 +178,8 @@ return 0;
 int
 main(int argc, char **argv)
 {
-sim_make_ROM_include ("VAX/ka655x.bin",  131072,  "VAX/vax_ka655x_bin.h", "vax_ka655x_bin");
-sim_make_ROM_include ("VAX/vmb.exe",      44544,  "VAX/vax780_vmb_exe.h", "vax780_vmb_exe");
-exit(0);
+int status = 0;
+status += sim_make_ROM_include ("VAX/ka655x.bin",  131072, 0xFF7673B6, "VAX/vax_ka655x_bin.h", "vax_ka655x_bin");
+status += sim_make_ROM_include ("VAX/vmb.exe",      44544, 0xFFC014CC, "VAX/vax780_vmb_exe.h", "vax780_vmb_exe");
+exit((status == 0) ? 0 : 1);
 }