diff --git a/3rdParty/mruby/Makefile b/3rdParty/mruby/Makefile
index 55988683b6..3d9637345f 100644
--- a/3rdParty/mruby/Makefile
+++ b/3rdParty/mruby/Makefile
@@ -53,7 +53,7 @@ DEBUG_MODE = 1
 ifeq ($(DEBUG_MODE),1)
 CFLAGS = -g
 else
-CFLAGS = -O3
+CFLAGS = -O2
 endif
 ALL_CFLAGS = -Wall -Werror-implicit-function-declaration $(CFLAGS)
 MAKE_FLAGS = --no-print-directory CC=$(CC) LL=$(LL)
diff --git a/3rdParty/mruby/mrblib/Makefile b/3rdParty/mruby/mrblib/Makefile
index ef60654fdc..31ffa99893 100644
--- a/3rdParty/mruby/mrblib/Makefile
+++ b/3rdParty/mruby/mrblib/Makefile
@@ -20,7 +20,7 @@ DEBUG_MODE = 1
 ifeq ($(DEBUG_MODE),1)
 CFLAGS = -g
 else
-CFLAGS = -O3
+CFLAGS = -O2
 endif
 INCLUDES = -I../src -I../include
 ALL_CFLAGS = -Wall -Werror-implicit-function-declaration $(CFLAGS)
diff --git a/3rdParty/mruby/src/Makefile b/3rdParty/mruby/src/Makefile
index fb5483a72b..f388203023 100644
--- a/3rdParty/mruby/src/Makefile
+++ b/3rdParty/mruby/src/Makefile
@@ -40,9 +40,9 @@ YACC = bison
 
 DEBUG_MODE = 1
 ifeq ($(DEBUG_MODE),1)
-CFLAGS = -g -O3
+CFLAGS = -g
 else
-CFLAGS = -O3
+CFLAGS = -O2
 endif
 ALL_CFLAGS = -Wall -Werror-implicit-function-declaration $(CFLAGS)
 MAKE_FLAGS = --no-print-directory CC=$(CC) LL=$(LL)
diff --git a/3rdParty/mruby/tools/mrbc/Makefile b/3rdParty/mruby/tools/mrbc/Makefile
index 7271a2fed6..69c4234ea7 100644
--- a/3rdParty/mruby/tools/mrbc/Makefile
+++ b/3rdParty/mruby/tools/mrbc/Makefile
@@ -34,7 +34,7 @@ DEBUG_MODE = 1
 ifeq ($(DEBUG_MODE),1)
 CFLAGS = -g
 else
-CFLAGS = -O3
+CFLAGS = -O2
 endif
 ALL_CFLAGS = -Wall -Werror-implicit-function-declaration $(CFLAGS)
 MAKE_FLAGS = --no-print-directory CC=$(CC) LL=$(LL)
diff --git a/3rdParty/mruby/tools/mruby/Makefile b/3rdParty/mruby/tools/mruby/Makefile
index 62d7cdd3f3..141693efdc 100644
--- a/3rdParty/mruby/tools/mruby/Makefile
+++ b/3rdParty/mruby/tools/mruby/Makefile
@@ -42,7 +42,7 @@ DEBUG_MODE = 1
 ifeq ($(DEBUG_MODE),1)
 CFLAGS = -g
 else
-CFLAGS = -O3
+CFLAGS = -O2
 endif
 ALL_CFLAGS = -Wall -Werror-implicit-function-declaration $(CFLAGS)
 MAKE_FLAGS = --no-print-directory CC=$(CC) LL=$(LL)