diff --git a/readme.md b/readme.md
index 3b141987b..42b5417ac 100644
--- a/readme.md
+++ b/readme.md
@@ -106,14 +106,14 @@ I am assuming you used the installer from https://sourceforge.net/projects/mingw
 1. Install MinGW-W64
 2. Use either *Run Terminal* from Start Menu or run *mingw-w64.bat* in the installation folder
 3. Navigate to the directory with ClassiCube's source code
-4. Enter `gcc -O2 -fno-math-errno *.c -o ClassiCube.exe -mwindows -lwinmm -limagehlp`
+4. Enter `gcc -fno-math-errno *.c -o ClassiCube.exe -mwindows -lwinmm -limagehlp`
 
 ##### Using MinGW
 I am assuming you used the installer from https://osdn.net/projects/mingw/
 1. Install MinGW. You need mingw32-base-bin and msys-base-bin packages.
 2. Run *msys.bat* in the *C:\MinGW\msys\1.0* folder.
 2. Navigate to the directory with ClassiCube's source code
-4. Enter `gcc -O2 -fno-math-errno *.c -o ClassiCube.exe -mwindows -lwinmm -limagehlp`
+4. Enter `gcc -fno-math-errno *.c -o ClassiCube.exe -mwindows -lwinmm -limagehlp`
 
 ##### Using TCC (Tiny C Compiler)
 I am assuming you used `tcc-0.9.27-win64-bin.zip` from https://bellard.org/tcc/
@@ -130,30 +130,30 @@ I am assuming you used `tcc-0.9.27-win64-bin.zip` from https://bellard.org/tcc/
 
 Install appropriate libs as required. For ubuntu these are: libx11-dev, libxi-dev and libgl1-mesa-dev
 
-```gcc -O2 -fno-math-errno *.c -o ClassiCube -rdynamic -lpthread -lX11 -lXi -lGL -ldl```
+```gcc -fno-math-errno *.c -o ClassiCube -rdynamic -lpthread -lX11 -lXi -lGL -ldl```
 
 ##### Cross compiling for Windows (32 bit):
 
-```i686-w64-mingw32-gcc -O2 -fno-math-errno *.c -o ClassiCube.exe -mwindows -lwinmm -limagehlp```
+```i686-w64-mingw32-gcc -fno-math-errno *.c -o ClassiCube.exe -mwindows -lwinmm -limagehlp```
 
 ##### Cross compiling for Windows (64 bit):
 
-```x86_64-w64-mingw32-gcc -O2 -fno-math-errno *.c -o ClassiCube.exe -mwindows -lwinmm -limagehlp```
+```x86_64-w64-mingw32-gcc -fno-math-errno *.c -o ClassiCube.exe -mwindows -lwinmm -limagehlp```
 
 ##### Raspberry Pi
 Although the regular linux compiliation flags will work fine, to take full advantage of the hardware:
 
-```gcc -O2 -fno-math-errno *.c -o ClassiCube -DCC_BUILD_RPI -rdynamic -lpthread -lX11 -lXi -lEGL -lGLESv2 -ldl```
+```gcc -fno-math-errno *.c -o ClassiCube -DCC_BUILD_RPI -rdynamic -lpthread -lX11 -lXi -lEGL -lGLESv2 -ldl```
 
 ## Compiling - macOS
 
 ##### Using gcc/clang (32 bit)
 
-```cc -O2 -fno-math-errno *.c -o ClassiCube -framework Carbon -framework AGL -framework OpenGL -framework IOKit```
+```cc -fno-math-errno *.c -o ClassiCube -framework Carbon -framework AGL -framework OpenGL -framework IOKit```
 
 ##### Using gcc/clang (64 bit)
 
-```cc -O2 -fno-math-errno *.c interop_cocoa.m -o ClassiCube -framework Cocoa -framework OpenGL -framework IOKit -lobjc```
+```cc -fno-math-errno *.c interop_cocoa.m -o ClassiCube -framework Cocoa -framework OpenGL -framework IOKit -lobjc```
 
 ## Compiling - for Android