diff --git a/components/salsa-macro-rules/src/setup_input_struct.rs b/components/salsa-macro-rules/src/setup_input_struct.rs
index 51cd482b..b506b28b 100644
--- a/components/salsa-macro-rules/src/setup_input_struct.rs
+++ b/components/salsa-macro-rules/src/setup_input_struct.rs
@@ -124,6 +124,9 @@ macro_rules! setup_input_struct {
             }
 
             impl $zalsa::SalsaStructInDb for $Struct {
+                fn lookup_ingredient_index(aux: &dyn $zalsa::JarAux) -> core::option::Option<$zalsa::IngredientIndex> {
+                    aux.lookup_jar_by_type(&<$zalsa_struct::JarImpl<$Configuration>>::default())
+                }
             }
 
             impl $Struct {
diff --git a/components/salsa-macro-rules/src/setup_interned_struct.rs b/components/salsa-macro-rules/src/setup_interned_struct.rs
index bf9d98f5..e8b8af18 100644
--- a/components/salsa-macro-rules/src/setup_interned_struct.rs
+++ b/components/salsa-macro-rules/src/setup_interned_struct.rs
@@ -141,6 +141,9 @@ macro_rules! setup_interned_struct {
             }
 
             impl $zalsa::SalsaStructInDb for $Struct<'_> {
+                fn lookup_ingredient_index(aux: &dyn $zalsa::JarAux) -> core::option::Option<$zalsa::IngredientIndex> {
+                    aux.lookup_jar_by_type(&<$zalsa_struct::JarImpl<$Configuration>>::default())
+                }
             }
 
             unsafe impl $zalsa::Update for $Struct<'_> {
diff --git a/components/salsa-macro-rules/src/setup_tracked_fn.rs b/components/salsa-macro-rules/src/setup_tracked_fn.rs
index 79ec96d5..ce5d313d 100644
--- a/components/salsa-macro-rules/src/setup_tracked_fn.rs
+++ b/components/salsa-macro-rules/src/setup_tracked_fn.rs
@@ -99,6 +99,9 @@ macro_rules! setup_tracked_fn {
                         $zalsa::IngredientCache::new();
 
                     impl $zalsa::SalsaStructInDb for $InternedData<'_> {
+                        fn lookup_ingredient_index(_aux: &dyn $zalsa::JarAux) -> core::option::Option<$zalsa::IngredientIndex> {
+                            None
+                        }
                     }
 
                     impl $zalsa::interned::Configuration for $Configuration {
@@ -199,7 +202,19 @@ macro_rules! setup_tracked_fn {
                     aux: &dyn $zalsa::JarAux,
                     first_index: $zalsa::IngredientIndex,
                 ) -> Vec<Box<dyn $zalsa::Ingredient>> {
+                    let struct_index = $zalsa::macro_if! {
+                        if $needs_interner {
+                            first_index.successor(0)
+                        } else {
+                            <$InternedData as $zalsa::SalsaStructInDb>::lookup_ingredient_index(aux)
+                                .expect(
+                                    "Salsa struct is passed as an argument of a tracked function, but its ingredient hasn't been added!"
+                                )
+                        }
+                    };
+
                     let fn_ingredient = <$zalsa::function::IngredientImpl<$Configuration>>::new(
+                        struct_index,
                         first_index,
                         aux,
                     );
@@ -219,6 +234,10 @@ macro_rules! setup_tracked_fn {
                         }
                     }
                 }
+
+                fn salsa_struct_type_id(&self) -> Option<core::any::TypeId> {
+                    None
+                }
             }
 
             #[allow(non_local_definitions)]
diff --git a/components/salsa-macro-rules/src/setup_tracked_struct.rs b/components/salsa-macro-rules/src/setup_tracked_struct.rs
index d0d42c6d..a783e376 100644
--- a/components/salsa-macro-rules/src/setup_tracked_struct.rs
+++ b/components/salsa-macro-rules/src/setup_tracked_struct.rs
@@ -152,6 +152,9 @@ macro_rules! setup_tracked_struct {
             }
 
             impl $zalsa::SalsaStructInDb for $Struct<'_> {
+                fn lookup_ingredient_index(aux: &dyn $zalsa::JarAux) -> core::option::Option<$zalsa::IngredientIndex> {
+                    aux.lookup_jar_by_type(&<$zalsa_struct::JarImpl<$Configuration>>::default())
+                }
             }
 
             impl $zalsa::TrackedStructInDb for $Struct<'_> {
diff --git a/src/accumulator.rs b/src/accumulator.rs
index b9355419..cd566f40 100644
--- a/src/accumulator.rs
+++ b/src/accumulator.rs
@@ -53,6 +53,10 @@ impl<A: Accumulator> Jar for JarImpl<A> {
     ) -> Vec<Box<dyn Ingredient>> {
         vec![Box::new(<IngredientImpl<A>>::new(first_index))]
     }
+
+    fn salsa_struct_type_id(&self) -> Option<std::any::TypeId> {
+        None
+    }
 }
 
 pub struct IngredientImpl<A: Accumulator> {
diff --git a/src/function.rs b/src/function.rs
index 07f13d49..b06be486 100644
--- a/src/function.rs
+++ b/src/function.rs
@@ -126,10 +126,10 @@ impl<C> IngredientImpl<C>
 where
     C: Configuration,
 {
-    pub fn new(index: IngredientIndex, aux: &dyn JarAux) -> Self {
+    pub fn new(struct_index: IngredientIndex, index: IngredientIndex, aux: &dyn JarAux) -> Self {
         Self {
             index,
-            memo_ingredient_index: aux.next_memo_ingredient_index(index),
+            memo_ingredient_index: aux.next_memo_ingredient_index(struct_index, index),
             lru: Default::default(),
             deleted_entries: Default::default(),
         }
diff --git a/src/ingredient.rs b/src/ingredient.rs
index 383fdc6b..8a46205d 100644
--- a/src/ingredient.rs
+++ b/src/ingredient.rs
@@ -23,10 +23,33 @@ pub trait Jar: Any {
         aux: &dyn JarAux,
         first_index: IngredientIndex,
     ) -> Vec<Box<dyn Ingredient>>;
+
+    /// If this jar's first ingredient is a salsa struct, return its `TypeId`
+    fn salsa_struct_type_id(&self) -> Option<TypeId>;
 }
 
+/// Methods on the Salsa database available to jars while they are creating their ingredients.
 pub trait JarAux {
-    fn next_memo_ingredient_index(&self, ingredient_index: IngredientIndex) -> MemoIngredientIndex;
+    /// Return index of first ingredient from `jar` (based on the dynamic type of `jar`).
+    /// Returns `None` if the jar has not yet been added.
+    /// Used by tracked functions to lookup the ingredient index for the salsa struct they take as argument.
+    fn lookup_jar_by_type(&self, jar: &dyn Jar) -> Option<IngredientIndex>;
+
+    /// Returns the memo ingredient index that should be used to attach data from the given tracked function
+    /// to the given salsa struct (which the fn accepts as argument).
+    ///
+    /// The memo ingredient indices for a given function must be distinct from the memo indices
+    /// of all other functions that take the same salsa struct.
+    ///
+    /// # Parameters
+    ///
+    /// * `struct_ingredient_index`, the index of the salsa struct the memo will be attached to
+    /// * `ingredient_index`, the index of the tracked function whose data is stored in the memo
+    fn next_memo_ingredient_index(
+        &self,
+        struct_ingredient_index: IngredientIndex,
+        ingredient_index: IngredientIndex,
+    ) -> MemoIngredientIndex;
 }
 
 pub trait Ingredient: Any + std::fmt::Debug + Send + Sync {
diff --git a/src/input.rs b/src/input.rs
index fdad27ac..4b82ef2f 100644
--- a/src/input.rs
+++ b/src/input.rs
@@ -1,4 +1,8 @@
-use std::{any::Any, fmt, ops::DerefMut};
+use std::{
+    any::{Any, TypeId},
+    fmt,
+    ops::DerefMut,
+};
 
 pub mod input_field;
 pub mod setter;
@@ -60,6 +64,10 @@ impl<C: Configuration> Jar for JarImpl<C> {
             }))
             .collect()
     }
+
+    fn salsa_struct_type_id(&self) -> Option<std::any::TypeId> {
+        Some(TypeId::of::<<C as Configuration>::Struct>())
+    }
 }
 
 pub struct IngredientImpl<C: Configuration> {
diff --git a/src/interned.rs b/src/interned.rs
index 0c6d32cd..f6767fb1 100644
--- a/src/interned.rs
+++ b/src/interned.rs
@@ -9,6 +9,7 @@ use crate::table::Slot;
 use crate::zalsa::IngredientIndex;
 use crate::zalsa_local::QueryOrigin;
 use crate::{Database, DatabaseKeyIndex, Id};
+use std::any::TypeId;
 use std::fmt;
 use std::hash::{BuildHasher, Hash, Hasher};
 use std::marker::PhantomData;
@@ -92,6 +93,10 @@ impl<C: Configuration> Jar for JarImpl<C> {
     ) -> Vec<Box<dyn Ingredient>> {
         vec![Box::new(IngredientImpl::<C>::new(first_index)) as _]
     }
+
+    fn salsa_struct_type_id(&self) -> Option<std::any::TypeId> {
+        Some(TypeId::of::<<C as Configuration>::Struct<'static>>())
+    }
 }
 
 impl<C> IngredientImpl<C>
diff --git a/src/salsa_struct.rs b/src/salsa_struct.rs
index fcf7920a..8674dc12 100644
--- a/src/salsa_struct.rs
+++ b/src/salsa_struct.rs
@@ -1 +1,5 @@
-pub trait SalsaStructInDb {}
+use crate::{plumbing::JarAux, IngredientIndex};
+
+pub trait SalsaStructInDb {
+    fn lookup_ingredient_index(aux: &dyn JarAux) -> Option<IngredientIndex>;
+}
diff --git a/src/tracked_struct.rs b/src/tracked_struct.rs
index 540bb765..8cca21e9 100644
--- a/src/tracked_struct.rs
+++ b/src/tracked_struct.rs
@@ -1,4 +1,4 @@
-use std::{fmt, hash::Hash, marker::PhantomData, ops::DerefMut};
+use std::{any::TypeId, fmt, hash::Hash, marker::PhantomData, ops::DerefMut};
 
 use crossbeam::{atomic::AtomicCell, queue::SegQueue};
 use tracked_field::FieldIngredientImpl;
@@ -112,6 +112,10 @@ impl<C: Configuration> Jar for JarImpl<C> {
             }))
             .collect()
     }
+
+    fn salsa_struct_type_id(&self) -> Option<TypeId> {
+        Some(TypeId::of::<<C as Configuration>::Struct<'static>>())
+    }
 }
 
 pub trait TrackedStructInDb: SalsaStructInDb {
@@ -501,7 +505,8 @@ where
         // and the code that references the memo-table has a read-lock.
         let memo_table = unsafe { (*data).take_memo_table() };
         for (memo_ingredient_index, memo) in memo_table.into_memos() {
-            let ingredient_index = zalsa.ingredient_index_for_memo(memo_ingredient_index);
+            let ingredient_index =
+                zalsa.ingredient_index_for_memo(self.ingredient_index, memo_ingredient_index);
 
             let executor = DatabaseKeyIndex {
                 ingredient_index,
diff --git a/src/zalsa.rs b/src/zalsa.rs
index 2f8fa95f..b21923d4 100644
--- a/src/zalsa.rs
+++ b/src/zalsa.rs
@@ -1,5 +1,5 @@
 use append_only_vec::AppendOnlyVec;
-use parking_lot::Mutex;
+use parking_lot::{Mutex, RwLock};
 use rustc_hash::FxHashMap;
 use std::any::{Any, TypeId};
 use std::marker::PhantomData;
@@ -119,8 +119,10 @@ pub struct Zalsa {
 
     nonce: Nonce<StorageNonce>,
 
-    /// Number of memo ingredient indices created by calls to [`next_memo_ingredient_index`](`Self::next_memo_ingredient_index`)
-    memo_ingredients: Mutex<Vec<IngredientIndex>>,
+    /// Map from the [`IngredientIndex::as_usize`][] of a salsa struct to a list of
+    /// [ingredient-indices](`IngredientIndex`) for tracked functions that have this salsa struct
+    /// as input.
+    memo_ingredient_indices: RwLock<Vec<Vec<IngredientIndex>>>,
 
     /// Map from the type-id of an `impl Jar` to the index of its first ingredient.
     /// This is using a `Mutex<FxHashMap>` (versus, say, a `FxDashMap`)
@@ -152,7 +154,7 @@ impl Zalsa {
             ingredients_vec: AppendOnlyVec::new(),
             ingredients_requiring_reset: AppendOnlyVec::new(),
             runtime: Runtime::default(),
-            memo_ingredients: Default::default(),
+            memo_ingredient_indices: Default::default(),
         }
     }
 
@@ -186,11 +188,20 @@ impl Zalsa {
         {
             let jar_type_id = jar.type_id();
             let mut jar_map = self.jar_map.lock();
-            *jar_map
-            .entry(jar_type_id)
-            .or_insert_with(|| {
-                let index = IngredientIndex::from(self.ingredients_vec.len());
-                let ingredients = jar.create_ingredients(self, index);
+            let mut should_create = false;
+            // First record the index we will use into the map and then go and create the ingredients.
+            // Those ingredients may invoke methods on the `JarAux` trait that read from this map
+            // to lookup ingredient indices for already created jars.
+            //
+            // Note that we still hold the lock above so only one jar is being created at a time and hence
+            // ingredient indices cannot overlap.
+            let index = *jar_map.entry(jar_type_id).or_insert_with(|| {
+                should_create = true;
+                IngredientIndex::from(self.ingredients_vec.len())
+            });
+            if should_create {
+                let aux = JarAuxImpl(self, &jar_map);
+                let ingredients = jar.create_ingredients(&aux, index);
                 for ingredient in ingredients {
                     let expected_index = ingredient.ingredient_index();
 
@@ -198,9 +209,7 @@ impl Zalsa {
                         self.ingredients_requiring_reset.push(expected_index);
                     }
 
-                    let actual_index = self
-                        .ingredients_vec
-                        .push(ingredient);
+                    let actual_index = self.ingredients_vec.push(ingredient);
                     assert_eq!(
                         expected_index.as_usize(),
                         actual_index,
@@ -209,10 +218,10 @@ impl Zalsa {
                         expected_index,
                         actual_index,
                     );
-
                 }
-                index
-            })
+            }
+
+            index
         }
     }
 
@@ -290,15 +299,34 @@ impl Zalsa {
 
     pub(crate) fn ingredient_index_for_memo(
         &self,
+        struct_ingredient_index: IngredientIndex,
         memo_ingredient_index: MemoIngredientIndex,
     ) -> IngredientIndex {
-        self.memo_ingredients.lock()[memo_ingredient_index.as_usize()]
+        self.memo_ingredient_indices.read()[struct_ingredient_index.as_usize()]
+            [memo_ingredient_index.as_usize()]
     }
 }
 
-impl JarAux for Zalsa {
-    fn next_memo_ingredient_index(&self, ingredient_index: IngredientIndex) -> MemoIngredientIndex {
-        let mut memo_ingredients = self.memo_ingredients.lock();
+struct JarAuxImpl<'a>(&'a Zalsa, &'a FxHashMap<TypeId, IngredientIndex>);
+
+impl JarAux for JarAuxImpl<'_> {
+    fn lookup_jar_by_type(&self, jar: &dyn Jar) -> Option<IngredientIndex> {
+        self.1.get(&jar.type_id()).map(ToOwned::to_owned)
+    }
+
+    fn next_memo_ingredient_index(
+        &self,
+        struct_ingredient_index: IngredientIndex,
+        ingredient_index: IngredientIndex,
+    ) -> MemoIngredientIndex {
+        let mut memo_ingredients = self.0.memo_ingredient_indices.write();
+        let idx = struct_ingredient_index.as_usize();
+        let memo_ingredients = if let Some(memo_ingredients) = memo_ingredients.get_mut(idx) {
+            memo_ingredients
+        } else {
+            memo_ingredients.resize_with(idx + 1, Vec::new);
+            memo_ingredients.get_mut(idx).unwrap()
+        };
         let mi = MemoIngredientIndex(u32::try_from(memo_ingredients.len()).unwrap());
         memo_ingredients.push(ingredient_index);
         mi
diff --git a/tests/tracked_fn_multiple_args.rs b/tests/tracked_fn_multiple_args.rs
new file mode 100644
index 00000000..7c014356
--- /dev/null
+++ b/tests/tracked_fn_multiple_args.rs
@@ -0,0 +1,25 @@
+//! Test that a `tracked` fn on multiple salsa struct args
+//! compiles and executes successfully.
+
+#[salsa::input]
+struct MyInput {
+    field: u32,
+}
+
+#[salsa::interned]
+struct MyInterned<'db> {
+    field: u32,
+}
+
+#[salsa::tracked]
+fn tracked_fn<'db>(db: &'db dyn salsa::Database, input: MyInput, interned: MyInterned<'db>) -> u32 {
+    input.field(db) + interned.field(db)
+}
+
+#[test]
+fn execute() {
+    let db = salsa::DatabaseImpl::new();
+    let input = MyInput::new(&db, 22);
+    let interned = MyInterned::new(&db, 33);
+    assert_eq!(tracked_fn(&db, input, interned), 55);
+}