diff --git a/docs/mold.md b/docs/mold.md
index 2099c46f97..19e7c25b3c 100644
--- a/docs/mold.md
+++ b/docs/mold.md
@@ -467,13 +467,13 @@ but as `-o magic`.
   The `--no-as-needed` option restores the default behavior for subsequent
   files.
 
-* `--build-id`=[ `md5` | `sha1` | `sha256` | `uuid` | `0x`_hexstring_ | `none` ]:
+* `--build-id`=[ `md5` | `sha1` | `sha256` | `fast` | `uuid` | `0x`_hexstring_ | `none` ]:
   Create a `.note.gnu.build-id` section containing a byte string to uniquely
   identify an output file. `sha256` compute a 256-bit cryptographic hash of an
   output file and set it to build-id. `md5` and `sha1` compute the same hash
   but truncate it to 128 and 160 bits, respectively, before setting it to
   build-id. `uuid` sets a random 128-bit UUID. `0x`_hexstring_ sets
-  _hexstring_.
+  _hexstring_. `fast` is a synonym for `sha256`.
 
 * `--build-id`:
   Synonym for `--build-id=sha256`.
diff --git a/elf/cmdline.cc b/elf/cmdline.cc
index 64a2ad90b9..12a745500c 100644
--- a/elf/cmdline.cc
+++ b/elf/cmdline.cc
@@ -72,7 +72,7 @@ inline const char helpmsg[] = R"(
     --no-apply-dynamic-relocs
   --as-needed                 Only set DT_NEEDED if used
     --no-as-needed
-  --build-id [none,md5,sha1,sha256,uuid,HEXSTRING]
+  --build-id [none,md5,sha1,sha256,fast,uuid,HEXSTRING]
                               Generate build ID
     --no-build-id
   --chroot DIR                Set a given path to the root directory
@@ -1232,7 +1232,7 @@ std::vector<std::string> parse_nonpositional_args(Context<E> &ctx) {
       } else if (arg == "sha1") {
         ctx.arg.build_id.kind = BuildId::HASH;
         ctx.arg.build_id.hash_size = 20;
-      } else if (arg == "sha256") {
+      } else if (arg == "sha256" || arg == "fast") {
         ctx.arg.build_id.kind = BuildId::HASH;
         ctx.arg.build_id.hash_size = 32;
       } else if (arg.starts_with("0x") || arg.starts_with("0X")) {
diff --git a/test/elf/build-id.sh b/test/elf/build-id.sh
index acff861e9a..d23109251c 100755
--- a/test/elf/build-id.sh
+++ b/test/elf/build-id.sh
@@ -18,5 +18,8 @@ readelf -n $t/exe | grep -q 'GNU.*0x00000014.*NT_GNU_BUILD_ID'
 $CC -B. -o $t/exe $t/a.c -Wl,-build-id=sha256
 readelf -n $t/exe | grep -q 'GNU.*0x00000020.*NT_GNU_BUILD_ID'
 
+$CC -B. -o $t/exe $t/a.c -Wl,-build-id=fast
+readelf -n $t/exe | grep -q 'GNU.*0x00000020.*NT_GNU_BUILD_ID'
+
 $CC -B. -o $t/exe $t/a.c -Wl,-build-id=0xdeadbeefdeadbeef
 readelf -n $t/exe | grep -q 'Build ID: deadbeefdeadbeef'