diff --git a/tools/ci/test_build_system.sh b/tools/ci/test_build_system.sh
index ebe459dd5..0239a1029 100755
--- a/tools/ci/test_build_system.sh
+++ b/tools/ci/test_build_system.sh
@@ -288,6 +288,25 @@ function run_tests()
     ( make 2>&1 | grep "does not fit in configured flash size 1MB" ) || failure "Build didn't fail with expected flash size failure message"
     mv sdkconfig.bak sdkconfig
 
+    print_status "Flash size is correctly set in the bootloader image header"
+    # Build with the default 2MB setting
+    rm sdkconfig
+    make defconfig && make bootloader || failure "Failed to build bootloader"
+    bin_header_match build/bootloader/bootloader.bin "0210"
+    # Change to 4MB
+    echo "CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y" > sdkconfig
+    make defconfig && make bootloader || failure "Failed to build bootloader"
+    bin_header_match build/bootloader/bootloader.bin "0220"
+    # Change to QIO, bootloader should still be DIO (will change to QIO in 2nd stage bootloader)
+    echo "CONFIG_FLASHMODE_QIO=y" > sdkconfig
+    make defconfig && make bootloader || failure "Failed to build bootloader"
+    bin_header_match build/bootloader/bootloader.bin "0210"
+    # Change to 80 MHz
+    echo "CONFIG_ESPTOOLPY_FLASHFREQ_80M=y" > sdkconfig
+    make defconfig && make bootloader || failure "Failed to build bootloader"
+    bin_header_match build/bootloader/bootloader.bin "021f"
+    rm sdkconfig
+
     print_status "sdkconfig should have contents of all files: sdkconfig, sdkconfig.defaults, sdkconfig.defaults.IDF_TARGET"
     make clean > /dev/null;
     rm -f sdkconfig.defaults;
@@ -491,5 +510,17 @@ function clean_build_dir()
     rm -rf --preserve-root ${BUILD}/*
 }
 
+# check the bytes 3-4 of the binary image header. e.g.:
+#   bin_header_match app.bin 0210
+function bin_header_match()
+{
+    expected=$2
+    filename=$1
+    actual=$(xxd -s 2 -l 2 -ps $1)
+    if [ ! "$expected" = "$actual" ]; then
+        failure "Incorrect binary image header, expected $expected got $actual"
+    fi
+}
+
 cd ${TESTDIR}
 run_tests
diff --git a/tools/ci/test_build_system_cmake.sh b/tools/ci/test_build_system_cmake.sh
index 339aa008e..00b15274b 100755
--- a/tools/ci/test_build_system_cmake.sh
+++ b/tools/ci/test_build_system_cmake.sh
@@ -595,6 +595,31 @@ endmenu\n" >> ${IDF_PATH}/Kconfig
     rm idf_project.yml
     git checkout main/main.c
 
+    print_status "Build fails if partitions don't fit in flash"
+    sed -i.bak "s/CONFIG_ESPTOOLPY_FLASHSIZE.\+//" sdkconfig  # remove all flashsize config
+    echo "CONFIG_ESPTOOLPY_FLASHSIZE_1MB=y" >> sdkconfig     # introduce undersize flash
+    ( idf.py build 2>&1 | grep "does not fit in configured flash size 1MB" ) || failure "Build didn't fail with expected flash size failure message"
+    mv sdkconfig.bak sdkconfig
+
+    print_status "Flash size is correctly set in the bootloader image header"
+    # Build with the default 2MB setting
+    rm sdkconfig
+    idf.py bootloader || failure "Failed to build bootloader"
+    bin_header_match build/bootloader/bootloader.bin "0210"
+    # Change to 4MB
+    echo "CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y" > sdkconfig
+    idf.py bootloader || failure "Failed to build bootloader"
+    bin_header_match build/bootloader/bootloader.bin "0220"
+    # Change to QIO, bootloader should still be DIO (will change to QIO in 2nd stage bootloader)
+    echo "CONFIG_FLASHMODE_QIO=y" > sdkconfig
+    idf.py bootloader || failure "Failed to build bootloader"
+    bin_header_match build/bootloader/bootloader.bin "0210"
+    # Change to 80 MHz
+    echo "CONFIG_ESPTOOLPY_FLASHFREQ_80M=y" > sdkconfig
+    idf.py bootloader || failure "Failed to build bootloader"
+    bin_header_match build/bootloader/bootloader.bin "021f"
+    rm sdkconfig
+
     print_status "All tests completed"
     if [ -n "${FAILURES}" ]; then
         echo "Some failures were detected:"
@@ -722,5 +747,17 @@ function clean_build_dir()
     rm -rf $PRESERVE_ROOT_ARG ${BUILD}/* ${BUILD}/.*
 }
 
+# check the bytes 3-4 of the binary image header. e.g.:
+#   bin_header_match app.bin 0210
+function bin_header_match()
+{
+    expected=$2
+    filename=$1
+    actual=$(xxd -s 2 -l 2 -ps $1)
+    if [ ! "$expected" = "$actual" ]; then
+        failure "Incorrect binary image header, expected $expected got $actual"
+    fi
+}
+
 cd ${TESTDIR}
 run_tests