diff --git a/build/esp32/Makefile b/build/esp32/Makefile
index 75cce14..5fe7bdb 100644
--- a/build/esp32/Makefile
+++ b/build/esp32/Makefile
@@ -13,7 +13,8 @@ OBJEXT      := o
 
 ESP_FLAGS   := -DESP32 -DSPIDER_DISTRO_MICRO -DSPIDER_OS_NONE -mlongcalls -ffunction-sections -fdata-sections -fno-exceptions -fno-rtti
 
-CFLAGS      := -Wall -std=c++20 -DSPIDER_COMPILING $(ESP_FLAGS)
+# -O0: no optimizations, faster compilation during development
+CFLAGS      := -Wall -std=c++20 -O0 -DSPIDER_COMPILING $(ESP_FLAGS)
 LFLAGS      := -Wl,--gc-sections -mlongcalls
 INC         := -I../../src/
 
diff --git a/build/esp32/gen_makefile.py b/build/esp32/gen_makefile.py
index 7f7c5b4..f70d1a9 100644
--- a/build/esp32/gen_makefile.py
+++ b/build/esp32/gen_makefile.py
@@ -16,7 +16,8 @@ OBJEXT      := o
 
 ESP_FLAGS   := -DESP32 -DSPIDER_DISTRO_MICRO -DSPIDER_OS_NONE -mlongcalls -ffunction-sections -fdata-sections -fno-exceptions -fno-rtti
 
-CFLAGS      := -Wall -std=c++20 -DSPIDER_COMPILING {dollar}(ESP_FLAGS)
+# -O0: no optimizations, faster compilation during development
+CFLAGS      := -Wall -std=c++20 -O0 -DSPIDER_COMPILING {dollar}(ESP_FLAGS)
 LFLAGS      := -Wl,--gc-sections -mlongcalls
 INC         := -I../../src/