diff --git a/src/engine.rs b/src/engine.rs
index 44cd129a..5c39140f 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -24,7 +24,7 @@ use crate::stdlib::{
     string::{String, ToString},
 };
 use crate::syntax::CustomSyntax;
-use crate::utils::get_hasher;
+use crate::utils::{get_hasher, StraightHasherBuilder};
 use crate::{
     calc_native_fn_hash, Dynamic, EvalAltResult, FnPtr, ImmutableString, Module, Position, Scope,
     Shared, StaticVec,
@@ -476,7 +476,7 @@ impl<T: Into<Dynamic>> From<T> for Target<'_> {
 /// ## WARNING
 ///
 /// This type is volatile and may change.
-#[derive(Debug, Clone, Eq, PartialEq, Hash, Default)]
+#[derive(Debug, Clone, Default)]
 pub struct State {
     /// Normally, access to variables are parsed with a relative offset into the scope to avoid a lookup.
     /// In some situation, e.g. after running an `eval` statement, subsequent offsets become mis-aligned.
@@ -489,6 +489,8 @@ pub struct State {
     pub operations: u64,
     /// Number of modules loaded.
     pub modules: usize,
+    /// Cached lookup values for function hashes.
+    pub functions_cache: HashMap<u64, Option<CallableFunction>, StraightHasherBuilder>,
 }
 
 impl State {
@@ -1886,6 +1888,10 @@ impl Engine {
             });
 
         scope.rewind(prev_scope_len);
+        if mods.len() != prev_mods_len {
+            // If imports list is modified, clear the functions lookup cache
+            state.functions_cache.clear();
+        }
         mods.truncate(prev_mods_len);
         state.scope_level -= 1;
 
@@ -2365,6 +2371,8 @@ impl Engine {
                             } else {
                                 mods.push(name_def.name.clone(), module);
                             }
+                            // When imports list is modified, clear the functions lookup cache
+                            state.functions_cache.clear();
                         }
 
                         state.modules += 1;
diff --git a/src/fn_call.rs b/src/fn_call.rs
index bb8720cb..9b1500ef 100644
--- a/src/fn_call.rs
+++ b/src/fn_call.rs
@@ -170,14 +170,25 @@ impl Engine {
     ) -> Result<(Dynamic, bool), Box<EvalAltResult>> {
         self.inc_operations(state)?;
 
-        // Search for the native function
-        // First search registered functions (can override packages)
-        // Then search packages
-        let func = //lib.get_fn(hash_fn, pub_only)
-            self.global_namespace.get_fn(hash_fn, pub_only)
+        let func = state.functions_cache.get(&hash_fn).cloned();
+
+        let func = if let Some(ref f) = func {
+            f.as_ref()
+        } else {
+            // Search for the native function
+            // First search registered functions (can override packages)
+            // Then search packages
+            // lib.get_fn(hash_fn, pub_only)
+            let f = self
+                .global_namespace
+                .get_fn(hash_fn, pub_only)
                 .or_else(|| self.packages.get_fn(hash_fn))
                 .or_else(|| mods.get_fn(hash_fn));
 
+            state.functions_cache.insert(hash_fn, f.cloned());
+            f
+        };
+
         if let Some(func) = func {
             assert!(func.is_native());
 
@@ -370,6 +381,9 @@ impl Engine {
         let mut lib_merged: StaticVec<_>;
 
         let unified_lib = if let Some(ref env_lib) = fn_def.lib {
+            // If the library is modified, clear the functions lookup cache
+            state.functions_cache.clear();
+
             lib_merged = Default::default();
             lib_merged.push(env_lib.as_ref());
             lib_merged.extend(lib.iter().cloned());