diff --git a/src/families/family-mx1.c b/src/families/family-mx1.c
index 8cdcf81..dbbb8db 100644
--- a/src/families/family-mx1.c
+++ b/src/families/family-mx1.c
@@ -356,3 +356,7 @@ void print_mx1(unsigned cfg0, unsigned cfg1, unsigned cfg2, unsigned cfg3)
     else
         printf("                       VBuson pin: controlled by port\n");
 }
+
+unsigned word_mask_mx1(unsigned address, unsigned word) {
+    return word;
+}
diff --git a/src/families/family-mx3.c b/src/families/family-mx3.c
index 613e965..be09b05 100644
--- a/src/families/family-mx3.c
+++ b/src/families/family-mx3.c
@@ -382,3 +382,7 @@ void print_mx3(unsigned cfg0, unsigned cfg1, unsigned cfg2, unsigned cfg3)
     else
         printf("                       VBuson pin: controlled by port\n");
 }
+
+unsigned word_mask_mx3(unsigned address, unsigned word) {
+    return word;
+}
diff --git a/src/families/family-mz.c b/src/families/family-mz.c
index 769d5a9..f71a2de 100644
--- a/src/families/family-mz.c
+++ b/src/families/family-mz.c
@@ -374,3 +374,7 @@ void print_mz(unsigned cfg0, unsigned cfg1, unsigned cfg2, unsigned cfg3)
     else
         printf("                       USBID pin: controlled by port\n");
 }
+
+unsigned word_mask_mz(unsigned address, unsigned word) {
+    return word;
+}
diff --git a/src/families/family-xlp.c b/src/families/family-xlp.c
index cac0691..aa7ed27 100644
--- a/src/families/family-xlp.c
+++ b/src/families/family-xlp.c
@@ -410,3 +410,11 @@ void print_xlp(unsigned cfg0, unsigned cfg1, unsigned cfg2, unsigned cfg3)
     else
         printf("                       VBuson pin: controlled by port\n");
 }
+
+unsigned word_mask_xlp(unsigned address, unsigned word) {
+    // DEVCFG0's highest bit doesn't exist.
+    if (address == 0x9FC02FFC) {
+        return word & 0x7FFFFFFF;
+    }
+    return word;
+}
diff --git a/src/include/target.h b/src/include/target.h
index b84f5c7..8fb6ab3 100644
--- a/src/include/target.h
+++ b/src/include/target.h
@@ -15,6 +15,7 @@
 #include "adapter.h"
 
 typedef void print_func_t(unsigned cfg0, unsigned cfg1, unsigned cfg2, unsigned cfg3);
+typedef unsigned word_mask_func_t(unsigned address, unsigned word);
 
 typedef struct {
     const char      *name;
@@ -22,6 +23,7 @@ typedef struct {
     unsigned        devcfg_offset;
     unsigned        bytes_per_row;
     print_func_t    *print_devcfg;
+    word_mask_func_t *word_mask;
     const unsigned  *pe_code;
     unsigned        pe_nwords;
     unsigned        pe_version;
diff --git a/src/target.c b/src/target.c
index a07fed5..3f57395 100644
--- a/src/target.c
+++ b/src/target.c
@@ -29,6 +29,11 @@ extern print_func_t print_mx3;
 extern print_func_t print_mz;
 extern print_func_t print_xlp;
 
+extern word_mask_func_t word_mask_mx1;
+extern word_mask_func_t word_mask_mx3;
+extern word_mask_func_t word_mask_xlp;
+extern word_mask_func_t word_mask_mz;
+
 extern unsigned long open_retries;
 
 /*
@@ -37,16 +42,16 @@ extern unsigned long open_retries;
                     /*-Boot-Devcfg--Row---Print------Code--------Nwords-Version-*/
 static const
 family_t family_mx1 = { "mx1",
-                        3,  0x0bf0, 128,  print_mx1, pic32_pemx1, 422,  0x0301 };
+                        3,  0x0bf0, 128,  print_mx1, word_mask_mx1, pic32_pemx1, 422,  0x0301 };
 static const
 family_t family_xlp = { "xlp",
-                        12, 0x2ff0, 512,  print_xlp, pic32_pemx3, 1044, 0x0201 };
+                        12, 0x2ff0, 512,  print_xlp, word_mask_xlp, pic32_pemx3, 1044, 0x0201 };
 static const
 family_t family_mx3 = { "mx3",
-                        12, 0x2ff0, 512,  print_mx3, pic32_pemx3, 1044, 0x0201 };
+                        12, 0x2ff0, 512,  print_mx3, word_mask_mx3, pic32_pemx3, 1044, 0x0201 };
 static const
 family_t family_mz  = { "mz",
-                        80, 0xffc0, 2048, print_mz,  pic32_pemz,  1052, 0x0502 };
+                        80, 0xffc0, 2048, print_mz,  word_mask_mz,  pic32_pemz,  1052, 0x0502 };
 /*
  * This one is a special one for the bootloader. We have no idea what we're
  * programming, so set the values to the maximum out of all the others.
@@ -773,6 +778,7 @@ void target_verify_block(target_t *t, unsigned addr,
     t->adapter->read_data(t->adapter, addr, nwords, block);
     for (i=0; i<nwords; i++) {
         expected = data [i];
+        expected = t->family->word_mask(addr + (i<<2), expected);
         word = block [i];
         if (word != expected) {
             conprintf(_("\nerror at address %08X: file=%08X, mem=%08X\n"),