diff --git a/share/completions/gcc.fish b/share/completions/gcc.fish
index 512a0d23f..f7032cf6a 100644
--- a/share/completions/gcc.fish
+++ b/share/completions/gcc.fish
@@ -264,10 +264,15 @@ complete -c gcc -o dumpmachine -d 'Print the compiler’s target machine (for ex
 complete -c gcc -o dumpversion -d 'Print the compiler version (for example, 3.0,6.3 or 7)---and don’t do anything else'
 complete -c gcc -o dumpspecs -d 'Print the compiler’s built-in specs---and don’t do anything else'
 complete -c gcc -o feliminate-unused-debug-types -d 'Normally, when producing DWARF2 output, GCC will emit debugging information for all types declared in a compilation unit, regardless of whether or not they are actually used in that compilation unit'
+complete -c gcc -o O -d 'Optimize'
+complete -c gcc -o O1 -d 'Optimize'
 complete -c gcc -o O2 -d 'Optimize even more'
 complete -c gcc -o O3 -d 'Optimize yet more'
 complete -c gcc -o O0 -d 'Do not optimize'
 complete -c gcc -o Os -d 'Optimize for size'
+complete -c gcc -o Ofast -d 'Disregard strict standards compliance'
+complete -c gcc -o Og -d 'Optimize debugging experience'
+complete -c gcc -o Oz -d 'Optimize aggressively for size rather than speed'
 complete -c gcc -o fno-default-inline -d 'Do not make member functions inline by default merely because they are defined inside the class scope (C++ only)'
 complete -c gcc -o fno-defer-pop -d 'Always pop the arguments to each function call as soon as that function returns'
 complete -c gcc -o fforce-mem -d 'Force memory operands to be copied into registers before doing arithmetic on them'