diff --git a/ci/build.yml b/ci/build.yml
index 27aaa1ffe..c89127c59 100644
--- a/ci/build.yml
+++ b/ci/build.yml
@@ -108,6 +108,8 @@ build crypto:
 # TODO: add clang https://github.com/trezor/trezor-firmware/issues/44
 build legacy firmware:
   stage: build
+  variables:
+    MEMORY_PROTECT: "0"
   script:
     - cd legacy
     - pipenv run script/cibuild
@@ -123,6 +125,7 @@ build legacy firmware debug:
   stage: build
   variables:
     DEBUG_LINK: "1"
+    MEMORY_PROTECT: "0"
   script:
     - cd legacy
     - pipenv run script/cibuild
@@ -131,6 +134,7 @@ build legacy firmware bitcoinonly:
   stage: build
   variables:
     BITCOIN_ONLY: "1"
+    MEMORY_PROTECT: "0"
   script:
     - cd legacy
     - pipenv run script/cibuild
diff --git a/legacy/Makefile.include b/legacy/Makefile.include
index 1ddc13f47..65500c4b3 100644
--- a/legacy/Makefile.include
+++ b/legacy/Makefile.include
@@ -135,10 +135,12 @@ CFLAGS += -DU2F_ENABLED=1
 endif
 
 ifeq ($(MEMORY_PROTECT), 0)
-CFLAGS += -DMEMORY_PROTECT=0
+CFLAGS   += -DMEMORY_PROTECT=0
+CPUFLAGS += -DMEMORY_PROTECT=0
 $(info MEMORY_PROTECT=0)
 else
-CFLAGS += -DMEMORY_PROTECT=1
+CFLAGS   += -DMEMORY_PROTECT=1
+CPUFLAGS += -DMEMORY_PROTECT=1
 $(info MEMORY_PROTECT=1)
 endif
 
@@ -194,9 +196,9 @@ $(NAME).elf: $(OBJS) $(LDSCRIPT) $(LIBDEPS)
 	@printf "  LD      $@\n"
 	$(Q)$(LD) -o $(NAME).elf $(OBJS) $(LDLIBS) $(LDFLAGS)
 
-%.o: %.s Makefile
+%.o: %.S Makefile
 	@printf "  AS      $@\n"
-	$(Q)$(AS) $(CPUFLAGS) -o $@ $<
+	$(Q)$(CC) $(CPUFLAGS) -o $@ -c $<
 
 %.o: %.c Makefile
 	@printf "  CC      $@\n"
diff --git a/legacy/firmware/bl_check.c b/legacy/firmware/bl_check.c
index 218c3d0c0..b548fc603 100644
--- a/legacy/firmware/bl_check.c
+++ b/legacy/firmware/bl_check.c
@@ -26,6 +26,8 @@
 #include "memory.h"
 #include "util.h"
 
+#if MEMORY_PROTECT
+
 static int known_bootloader(int r, const uint8_t *hash) {
   if (r != 32) return 0;
   if (0 ==
@@ -126,6 +128,7 @@ static int known_bootloader(int r, const uint8_t *hash) {
     return 1;  // 1.8.0 shipped with fw 1.8.0 and 1.8.1
   return 0;
 }
+#endif
 
 void check_bootloader(void) {
 #if MEMORY_PROTECT
diff --git a/legacy/startup.s b/legacy/startup.S
similarity index 98%
rename from legacy/startup.s
rename to legacy/startup.S
index ce75ba1a7..f79646cad 100644
--- a/legacy/startup.s
+++ b/legacy/startup.S
@@ -19,6 +19,8 @@ memset_reg:
   .global reset_handler
   .type reset_handler, STT_FUNC
 reset_handler:
+
+#if MEMORY_PROTECT
 // we need to perform this in case an old bootloader
 // is starting the new firmware, these will be set incorrectly
   ldr r0, =0xE000ED08  // r0 = VTOR address
@@ -28,6 +30,7 @@ reset_handler:
   msr msp, r0          // set stack pointer
   dsb
   isb
+#endif
 
   ldr r0, =_ram_start // r0 - point to beginning of SRAM
   ldr r1, =_ram_end   // r1 - point to byte after the end of SRAM