diff --git a/docs/glossary.rst b/docs/glossary.rst
index 21f248166..486baadbb 100644
--- a/docs/glossary.rst
+++ b/docs/glossary.rst
@@ -231,7 +231,10 @@ Variables that kitty sets when running child programs
    Set to ``1`` when kitty is running a shell because of the ``--hold`` flag. Can
    be used to specialize shell behavior in the shell rc files as desired.
 
-.. envvar:: KITTY_NO_SIMD
+.. envvar:: KITTY_SIMD
 
-   Set it to any value to prevent kitty from using SIMD CPU vector
-   instructions.
+   Set it to ``128`` to use 128 bit vector registers, ``256`` to use 256 bit
+   vector registers or any other value to prevent kitty from using SIMD CPU
+   vector instructions. Warning, this overrides CPU capability detection so
+   will cause kitty to crash with SIGILL if your CPU does not support the
+   necessary SIMD extensions.
diff --git a/kitty/simd-string.c b/kitty/simd-string.c
index 8addb65dd..fa714533a 100644
--- a/kitty/simd-string.c
+++ b/kitty/simd-string.c
@@ -139,8 +139,10 @@ init_simd(void *x) {
     do_check();
 #endif
 #endif
-    if (getenv("KITTY_NO_SIMD")) {
-        has_avx2 = false; has_sse4_2 = false;
+    const char *simd_env = getenv("KITTY_SIMD");
+    if (simd_env) {
+        has_sse4_2 = strcmp(simd_env, "128") == 0;
+        has_avx2 = strcmp(simd_env, "256") == 0;
     }
 
 #undef do_check