diff --git a/tools/pio/pre_custom_esp32.py b/tools/pio/pre_custom_esp32.py
index 0061629ce..c43244b73 100644
--- a/tools/pio/pre_custom_esp32.py
+++ b/tools/pio/pre_custom_esp32.py
@@ -88,7 +88,7 @@ else:
 
 my_flags = env.ParseFlags(env['BUILD_FLAGS'])
 my_defines = my_flags.get("CPPDEFINES")
-env.Append(BUILD_FLAGS=custom_defines)
+env.Append(CXXFLAGS=custom_defines)
 #defines = {k: v for (k, v) in my_defines}
 
 print("\u001b[32m Custom PIO configuration check \u001b[0m")
diff --git a/tools/pio/pre_custom_esp32_IR.py b/tools/pio/pre_custom_esp32_IR.py
index 6bf934431..07e1bff33 100644
--- a/tools/pio/pre_custom_esp32_IR.py
+++ b/tools/pio/pre_custom_esp32_IR.py
@@ -85,7 +85,7 @@ else:
 
 my_flags = env.ParseFlags(env['BUILD_FLAGS'])
 my_defines = my_flags.get("CPPDEFINES")
-env.Append(BUILD_FLAGS=custom_defines)
+env.Append(CXXFLAGS=custom_defines)
 #defines = {k: v for (k, v) in my_defines}
 
 print("\u001b[32m Custom PIO configuration check \u001b[0m")
diff --git a/tools/pio/pre_custom_esp32c2.py b/tools/pio/pre_custom_esp32c2.py
index cc470b717..bdf2556c8 100644
--- a/tools/pio/pre_custom_esp32c2.py
+++ b/tools/pio/pre_custom_esp32c2.py
@@ -84,7 +84,7 @@ else:
 
 my_flags = env.ParseFlags(env['BUILD_FLAGS'])
 my_defines = my_flags.get("CPPDEFINES")
-env.Append(BUILD_FLAGS=custom_defines)
+env.Append(CXXFLAGS=custom_defines)
 #defines = {k: v for (k, v) in my_defines}
 
 print("\u001b[32m Custom PIO configuration check \u001b[0m")
diff --git a/tools/pio/pre_custom_esp32c6.py b/tools/pio/pre_custom_esp32c6.py
index 17b0a9632..feb04e6ba 100644
--- a/tools/pio/pre_custom_esp32c6.py
+++ b/tools/pio/pre_custom_esp32c6.py
@@ -86,7 +86,7 @@ else:
 
 my_flags = env.ParseFlags(env['BUILD_FLAGS'])
 my_defines = my_flags.get("CPPDEFINES")
-env.Append(BUILD_FLAGS=custom_defines)
+env.Append(CXXFLAGS=custom_defines)
 #defines = {k: v for (k, v) in my_defines}
 
 print("\u001b[32m Custom PIO configuration check \u001b[0m")
diff --git a/tools/pio/pre_custom_esp82xx.py b/tools/pio/pre_custom_esp82xx.py
index 39600161b..1d1768bd3 100644
--- a/tools/pio/pre_custom_esp82xx.py
+++ b/tools/pio/pre_custom_esp82xx.py
@@ -84,7 +84,7 @@ else:
 
 my_flags = env.ParseFlags(env['BUILD_FLAGS'])
 my_defines = my_flags.get("CPPDEFINES")
-env.Append(BUILD_FLAGS=custom_defines)
+env.Append(CXXFLAGS=custom_defines)
 #defines = {k: v for (k, v) in my_defines}
 
 print("\u001b[32m Custom PIO configuration check \u001b[0m")
diff --git a/tools/pio/pre_custom_esp82xx_IR.py b/tools/pio/pre_custom_esp82xx_IR.py
index 3e2556426..99cfa86bd 100644
--- a/tools/pio/pre_custom_esp82xx_IR.py
+++ b/tools/pio/pre_custom_esp82xx_IR.py
@@ -72,7 +72,7 @@ else:
 
 my_flags = env.ParseFlags(env['BUILD_FLAGS'])
 my_defines = my_flags.get("CPPDEFINES")
-env.Append(BUILD_FLAGS=custom_defines)
+env.Append(CXXFLAGS=custom_defines)
 #defines = {k: v for (k, v) in my_defines}
 
 print("\u001b[32m Custom PIO configuration check \u001b[0m")
diff --git a/tools/pio/pre_safeboot_esp32c2.py b/tools/pio/pre_safeboot_esp32c2.py
index 429b27940..c696729c0 100644
--- a/tools/pio/pre_safeboot_esp32c2.py
+++ b/tools/pio/pre_safeboot_esp32c2.py
@@ -47,7 +47,7 @@ else:
 
 my_flags = env.ParseFlags(env['BUILD_FLAGS'])
 my_defines = my_flags.get("CPPDEFINES")
-env.Append(BUILD_FLAGS=custom_defines)
+env.Append(CXXFLAGS=custom_defines)
 #defines = {k: v for (k, v) in my_defines}
 
 print("\u001b[32m Custom PIO configuration check \u001b[0m")