diff --git a/crates/core/flags/complete/fish.rs b/crates/core/flags/complete/fish.rs
index f8f7133bc..8952cdd38 100644
--- a/crates/core/flags/complete/fish.rs
+++ b/crates/core/flags/complete/fish.rs
@@ -6,11 +6,15 @@ use crate::flags::{defs::FLAGS, CompletionType};
 
 const TEMPLATE: &'static str = "complete -c rg !SHORT! -l !LONG! -d '!DOC!'";
 const TEMPLATE_NEGATED: &'static str =
-    "complete -c rg -l !NEGATED! -n '__fish_contains_opt !SHORT! !LONG!' -d '!DOC!'\n";
+    "complete -c rg -l !NEGATED! -n '__rg_contains_opt !LONG! !SHORT!' -d '!DOC!'\n";
 
 /// Generate completions for Fish.
+///
+/// Reference: <https://fishshell.com/docs/current/completions.html>
 pub(crate) fn generate() -> String {
     let mut out = String::new();
+    out.push_str(include_str!("prelude.fish"));
+    out.push('\n');
     for flag in FLAGS.iter() {
         let short = match flag.name_short() {
             None => "".to_string(),
@@ -55,6 +59,10 @@ pub(crate) fn generate() -> String {
         out.push_str(&completion);
 
         if let Some(negated) = flag.name_negated() {
+            let short = match flag.name_short() {
+                None => "".to_string(),
+                Some(byte) => char::from(byte).to_string(),
+            };
             out.push_str(
                 &TEMPLATE_NEGATED
                     .replace("!NEGATED!", &negated)
diff --git a/crates/core/flags/complete/prelude.fish b/crates/core/flags/complete/prelude.fish
new file mode 100644
index 000000000..6932f3e81
--- /dev/null
+++ b/crates/core/flags/complete/prelude.fish
@@ -0,0 +1,31 @@
+# Usage: __rg_contains_opt LONG [SHORT]
+function __rg_contains_opt --description 'Specialized __fish_contains_opt'
+    # Cache the config file because this function is called many times per
+    # completion attempt.
+    # The cache will persist for the entire shell session (even if the
+    # variable or the file contents change).
+    if not set -q __rg_config
+        set -g __rg_config
+        if set -qx RIPGREP_CONFIG_PATH
+            set __rg_config (
+                cat -- $RIPGREP_CONFIG_PATH 2>/dev/null \
+                | string trim \
+                | string match -rv '^$|^#'
+            )
+        end
+    end
+
+    set -l commandline (commandline -cpo) (commandline -ct) $__rg_config
+
+    if contains -- "--$argv[1]" $commandline
+        return 0
+    end
+
+    if set -q argv[2]
+        if string match -qr -- "^-[^-]*$argv[2]" $commandline
+            return 0
+        end
+    end
+
+    return 1
+end