diff --git a/build_helper/build_helper_configs.py b/build_helper/build_helper_configs.py
index c27d219..d01ca6e 100755
--- a/build_helper/build_helper_configs.py
+++ b/build_helper/build_helper_configs.py
@@ -78,28 +78,34 @@
                                 "%(_tbm_build_dir_)s/bin/"
                                 "bl2.bin "
                                 "-Binary -offset 0x200000 "
+                                "-fill 0xFF 0x200000 0x220000 "
                                 "%(_tbm_build_dir_)s/bin/"
                                 "tfm_s_ns_signed.bin "
-                                "-Binary -offset 0x220000 -o "
-                                "%(_tbm_build_dir_)s/bin/"
+                                "-Binary -offset 0x220000 "
+                                "-fill 0xFF 0x220000 0xA00000 "
+                                "-o %(_tbm_build_dir_)s/bin/"
                                 "tfm.hex -Intel")],
                    "musca_b1": [("srec_cat "
                                  "%(_tbm_build_dir_)s/bin/"
                                  "bl2.bin "
                                  "-Binary -offset 0xA000000 "
+                                 "-fill 0xFF 0xA000000 0xA020000 "
                                  "%(_tbm_build_dir_)s/bin/"
                                  "tfm_s_ns_signed.bin "
-                                 "-Binary -offset 0xA020000 -o "
-                                 "%(_tbm_build_dir_)s/bin/"
+                                 "-Binary -offset 0xA020000 "
+                                 "-fill 0xFF 0xA020000 0xA200000 "
+                                 "-o %(_tbm_build_dir_)s/bin/"
                                  "tfm.hex -Intel")],
                    "musca_s1": [("srec_cat "
                                  "%(_tbm_build_dir_)s/bin/"
                                  "bl2.bin "
                                  "-Binary -offset 0xA000000 "
+                                 "-fill 0xFF 0xA000000 0xA020000 "
                                  "%(_tbm_build_dir_)s/bin/"
                                  "tfm_s_ns_signed.bin "
-                                 "-Binary -offset 0xA020000 -o "
-                                 "%(_tbm_build_dir_)s/bin/"
+                                 "-Binary -offset 0xA020000 "
+                                 "-fill 0xFF 0xA020000 0xA200000 "
+                                 "-o %(_tbm_build_dir_)s/bin/"
                                  "tfm.hex -Intel")]
                    },