diff --git a/share/functions/__fish_cache_sourced_completions.fish b/share/functions/__fish_cache_sourced_completions.fish
new file mode 100644
index 000000000..41ba3bea9
--- /dev/null
+++ b/share/functions/__fish_cache_sourced_completions.fish
@@ -0,0 +1,45 @@
+function __fish_cache_sourced_completions
+    # Allow a `--name=foo` option which ends up in the filename.
+    argparse -s name= -- $argv
+    or return
+
+    set -q argv[1]
+    or return 1
+    
+    set -l cmd (command -s $argv[1])
+    or begin
+        # If we have no command, we can't get an mtime
+        # and so we can't cache
+        # The caller can more easily retry
+        return 127
+    end
+
+    set -l cachedir (__fish_make_cache_dir completions)
+    or return
+
+    set -l stampfile $cachedir/$argv[1].stamp
+    set -l compfile $cachedir/$argv[1].fish
+
+    set -l mtime (path mtime -- $cmd)
+
+    set -l cmtime 0
+    path is -rf -- $stampfile
+    and read cmtime < $stampfile
+
+    # If either the timestamp or the completion file don't exist,
+    # or the mtime differs, we rerun.
+    #
+    # That means we'll rerun if the command was up- or downgraded.
+    if path is -vrf -- $stampfile $compfile || test "$cmtime" -ne "$mtime" 2>/dev/null
+        $argv > $compfile
+        # If the command exited unsuccessfully, we assume it didn't work.
+        or return 2
+        echo -- $mtime > $stampfile
+    end
+
+    if path is -rf -- $compfile
+        source $compfile
+        return 0
+    end
+    return 3
+end