diff --git a/doc/man/crystal-build.adoc b/doc/man/crystal-build.adoc
index 5b0d5e3c0844..b75c8e84a11b 100644
--- a/doc/man/crystal-build.adoc
+++ b/doc/man/crystal-build.adoc
@@ -68,7 +68,7 @@ pass a --code-model flag to LLVM.
 Disable colored output.
 *--no-codegen*::
 Don't do code generation, just parse the file.
-*-o*::  Specify filename of output.
+*-o* _FILE_, *--output* _FILE_::  Specify filename of output.
 *--prelude*::
 Specify prelude to use. The default one initializes the garbage
 collector. You can also use --prelude=empty to use no preludes.
diff --git a/etc/completion.bash b/etc/completion.bash
index b64bd110a205..eb611851b76d 100644
--- a/etc/completion.bash
+++ b/etc/completion.bash
@@ -46,7 +46,7 @@ _crystal()
             ;;
         build)
             if [[ "${cur}" == -* ]] ; then
-                local opts="--cross-compile --debug --emit --error-on-warnings --exclude-warnings --ll --link-flags --mcpu --no-color --no-codegen --prelude --release --single-module --threads --target --verbose --warnings --help"
+                local opts="--cross-compile --debug --emit --error-on-warnings --exclude-warnings --ll --link-flags --mcpu --no-color --no-codegen --output --prelude --release --single-module --threads --target --verbose --warnings --help"
                 _crystal_compgen_options "${opts}" "${cur}"
             else
                 _crystal_compgen_sources "${cur}"
@@ -54,7 +54,7 @@ _crystal()
             ;;
         run)
             if [[ "${cur}" == -* ]] ; then
-                local opts="--debug --define --emit --error-on-warnings --exclude-warnings --format --help --ll --link-flags --mcpu --no-color --no-codegen --prelude --release --stats --single-module --threads --verbose --warnings"
+                local opts="--debug --define --emit --error-on-warnings --exclude-warnings --format --help --ll --link-flags --mcpu --no-color --no-codegen --output --prelude --release --stats --single-module --threads --verbose --warnings"
                 _crystal_compgen_options "${opts}" "${cur}"
             else
                 _crystal_compgen_sources "${cur}"
diff --git a/etc/completion.fish b/etc/completion.fish
index a74d6ecf3cac..5cc7f2dc2186 100644
--- a/etc/completion.fish
+++ b/etc/completion.fish
@@ -25,7 +25,7 @@ complete -c crystal -n "__fish_seen_subcommand_from build" -l error-on-warnings
 complete -c crystal -n "__fish_seen_subcommand_from build" -l exclude-warnings -d "Exclude warnings from path (default: lib)"
 complete -c crystal -n "__fish_seen_subcommand_from build" -l no-color -d "Disable colored output"
 complete -c crystal -n "__fish_seen_subcommand_from build" -l no-codegen -d "Don't do code generation"
-complete -c crystal -n "__fish_seen_subcommand_from build" -s o -d "Output filename"
+complete -c crystal -n "__fish_seen_subcommand_from build" -s o -l output -d "Output filename"
 complete -c crystal -n "__fish_seen_subcommand_from build" -l prelude -d "Use given file as prelude"
 complete -c crystal -n "__fish_seen_subcommand_from build" -l release -d "Compile in release mode"
 complete -c crystal -n "__fish_seen_subcommand_from build" -s s -l stats -d "Enable statistics output"
@@ -106,7 +106,7 @@ complete -c crystal -n "__fish_seen_subcommand_from run" -l error-on-warnings -d
 complete -c crystal -n "__fish_seen_subcommand_from run" -l exclude-warnings -d "Exclude warnings from path (default: lib)"
 complete -c crystal -n "__fish_seen_subcommand_from run" -l no-color -d "Disable colored output"
 complete -c crystal -n "__fish_seen_subcommand_from run" -l no-codegen -d "Don't do code generation"
-complete -c crystal -n "__fish_seen_subcommand_from run" -s o -d "Output filename"
+complete -c crystal -n "__fish_seen_subcommand_from run" -s o -l output -d "Output filename"
 complete -c crystal -n "__fish_seen_subcommand_from run" -l prelude -d "Use given file as prelude"
 complete -c crystal -n "__fish_seen_subcommand_from run" -l release -d "Compile in release mode"
 complete -c crystal -n "__fish_seen_subcommand_from run" -s s -l stats -d "Enable statistics output"
diff --git a/etc/completion.zsh b/etc/completion.zsh
index 0d9ff58a67c2..c8b3efe484cb 100644
--- a/etc/completion.zsh
+++ b/etc/completion.zsh
@@ -89,7 +89,7 @@ local -a shared_run_build; shared_run_build=(
   '(--mcpu)--mcpu[target specific cpu type]:' \
   '(--mattr)--mattr[target specific features]:' \
   "(--no-codegen)--no-codegen[don't do code generation]" \
-  '(-o)-o[output filename]:' \
+  '(-o --output)'{-o,--output}'[output filename]:' \
   '(--single-module)--single-module[generate a single llvm module]' \
   '(--threads)--threads[maximum number of threads to use]' \
   '(--verbose)--verbose[display executed commands]' \
diff --git a/src/compiler/crystal/command.cr b/src/compiler/crystal/command.cr
index cc6f39657f64..3c76bd89935f 100644
--- a/src/compiler/crystal/command.cr
+++ b/src/compiler/crystal/command.cr
@@ -508,7 +508,7 @@ class Crystal::Command
         opts.on("--no-codegen", "Don't do code generation") do
           compiler.no_codegen = true
         end
-        opts.on("-o ", "Output filename") do |an_output_filename|
+        opts.on("-o FILE", "--output FILE", "Output filename") do |an_output_filename|
           opt_output_filename = an_output_filename
           specified_output = true
         end