diff --git a/components/app_update/CMakeLists.txt b/components/app_update/CMakeLists.txt
index a8492e351a..74c0d88fed 100644
--- a/components/app_update/CMakeLists.txt
+++ b/components/app_update/CMakeLists.txt
@@ -49,7 +49,8 @@ if(NOT BOOTLOADER_BUILD)
         set(otatool_py ${python} ${COMPONENT_DIR}/otatool.py)
 
         set(esptool_args "--esptool-args;before=${CONFIG_ESPTOOLPY_BEFORE};after=${CONFIG_ESPTOOLPY_AFTER}")
-        set(otatool_args "--partition-table-file;${PARTITION_CSV_PATH};--partition-table-offset;${PARTITION_TABLE_OFFSET}")
+        set(otatool_args "--partition-table-file;${PARTITION_CSV_PATH}"
+                         "--partition-table-offset;${PARTITION_TABLE_OFFSET}")
         idf_component_get_property(esptool_py_dir esptool_py COMPONENT_DIR)
 
         add_custom_target(read_otadata DEPENDS "${PARTITION_CSV_PATH}"
diff --git a/components/esptool_py/get_port_args.cmake b/components/esptool_py/get_port_args.cmake
index e70f131046..90f5258611 100644
--- a/components/esptool_py/get_port_args.cmake
+++ b/components/esptool_py/get_port_args.cmake
@@ -3,7 +3,8 @@
 # without needing a CMake re-run)
 set(ESPPORT $ENV{ESPPORT})
 if(NOT ESPPORT)
-    message("Note: ${SERIAL_TOOL} will search for a serial port. To specify a port, set the ESPPORT environment variable.")
+    message("Note: ${SERIAL_TOOL} will search for a serial port. "
+            "To specify a port, set the ESPPORT environment variable.")
 else()
     set(port_arg "-p ${ESPPORT}")
 endif()
diff --git a/components/esptool_py/run_cmd.cmake b/components/esptool_py/run_cmd.cmake
deleted file mode 100644
index a5620a3420..0000000000
--- a/components/esptool_py/run_cmd.cmake
+++ /dev/null
@@ -1,15 +0,0 @@
-if(NOT IDF_PATH)
-    message(FATAL_ERROR "IDF_PATH not set.")
-endif()
-include("${IDF_PATH}/tools/cmake/utilities.cmake")
-spaces2list(CMD)
-
-execute_process(COMMAND ${CMD}
-    WORKING_DIRECTORY "${WORKING_DIRECTORY}"
-    RESULT_VARIABLE result
-    )
-
-if(${result})
-    # No way to have CMake silently fail, unfortunately
-    message(FATAL_ERROR "${SERIAL_TOOL} failed")
-endif()
diff --git a/components/esptool_py/run_serial_tool.cmake b/components/esptool_py/run_serial_tool.cmake
index 04d3f5afdf..ce8bf93d98 100644
--- a/components/esptool_py/run_serial_tool.cmake
+++ b/components/esptool_py/run_serial_tool.cmake
@@ -1,19 +1,51 @@
-# A CMake script to run esptool commands from within ninja or make
-# or another cmake-based build runner
-#
-# (Needed to expand environment variables, for backwards compatibility.)
+# A CMake script to run serial tool commands supporting ESPPORT and
+# ESPBAUD environment variables from within ninja or make or another
+# cmake-based build runner.
 #
 # It is recommended to NOT USE this CMake script if you have the option of
-# running esptool.py directly. This script exists only for use inside CMake builds.
-#
+# running the tool directly. This script exists only for use inside CMake builds.
 cmake_minimum_required(VERSION 3.5)
 
+if(NOT IDF_PATH)
+    message(FATAL_ERROR "IDF_PATH not set.")
+endif()
+
 if(NOT SERIAL_TOOL OR NOT SERIAL_TOOL_ARGS)
     message(FATAL_ERROR "SERIAL_TOOL and SERIAL_TOOL_ARGS must "
         "be specified on the CMake command line. For direct execution, it is "
         "strongly recommended to run ${SERIAL_TOOL} directly.")
 endif()
 
-include("${CMAKE_CURRENT_LIST_DIR}/get_port_args.cmake")
-set(CMD "${SERIAL_TOOL} ${port_arg} ${baud_arg} ${SERIAL_TOOL_ARGS}")
-include("${CMAKE_CURRENT_LIST_DIR}/run_cmd.cmake")
+# Main purpose of this script: we can't expand these environment variables in the main IDF CMake build,
+# because we want to expand them at flashing time not at CMake runtime (so they can change
+# without needing a CMake re-run)
+set(ESPPORT $ENV{ESPPORT})
+if(NOT ESPPORT)
+    message("Note: ${SERIAL_TOOL} will search for a serial port. "
+            "To specify a port, set the ESPPORT environment variable.")
+else()
+    set(port_arg "-p ${ESPPORT}")
+endif()
+
+set(ESPBAUD $ENV{ESPBAUD})
+if(NOT ESPBAUD)
+    message("Note: ${SERIAL_TOOL} will attempt to set baud rate automatically. "
+            "To specify a baud rate, set the ESPBAUD environment variable.")
+else()
+    set(baud_arg "-b ${ESPBAUD}")
+endif()
+
+set(serial_tool_cmd "${SERIAL_TOOL} ${port_arg} ${baud_arg} ${SERIAL_TOOL_ARGS}")
+
+include("${IDF_PATH}/tools/cmake/utilities.cmake")
+spaces2list(serial_tool_cmd)
+
+execute_process(COMMAND ${serial_tool_cmd}
+    WORKING_DIRECTORY "${WORKING_DIRECTORY}"
+    RESULT_VARIABLE result
+    )
+
+if(${result})
+    # No way to have CMake silently fail, unfortunately
+    message(FATAL_ERROR "${SERIAL_TOOL} failed")
+endif()