diff --git a/bindings/rust/src/ffi.rs b/bindings/rust/src/ffi.rs
index 7f7a205b..d812e8cd 100644
--- a/bindings/rust/src/ffi.rs
+++ b/bindings/rust/src/ffi.rs
@@ -121,9 +121,15 @@ pub unsafe extern "C" fn mmio_read_callback_proxy<D, F>(
 where
     F: FnMut(&mut crate::Unicorn<D>, u64, usize) -> u64,
 {
+    if user_data.is_null() {
+        return 0;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return 0;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc, offset, size)
@@ -138,9 +144,15 @@ pub unsafe extern "C" fn mmio_write_callback_proxy<D, F>(
 ) where
     F: FnMut(&mut crate::Unicorn<D>, u64, usize, u64),
 {
+    if user_data.is_null() {
+        return;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc, offset, size, value);
@@ -154,9 +166,15 @@ pub unsafe extern "C" fn code_hook_proxy<D, F>(
 ) where
     F: FnMut(&mut crate::Unicorn<D>, u64, u32),
 {
+    if user_data.is_null() {
+        return;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc, address, size);
@@ -170,9 +188,15 @@ pub unsafe extern "C" fn block_hook_proxy<D, F>(
 ) where
     F: FnMut(&mut crate::Unicorn<D>, u64, u32),
 {
+    if user_data.is_null() {
+        return;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc, address, size);
@@ -189,9 +213,15 @@ pub unsafe extern "C" fn mem_hook_proxy<D, F>(
 where
     F: FnMut(&mut crate::Unicorn<D>, MemType, u64, usize, i64) -> bool,
 {
+    if user_data.is_null() {
+        return false;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return false;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc, mem_type, address, size as usize, value)
@@ -204,9 +234,15 @@ pub unsafe extern "C" fn intr_hook_proxy<D, F>(
 ) where
     F: FnMut(&mut crate::Unicorn<D>, u32),
 {
+    if user_data.is_null() {
+        return;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc, value);
@@ -221,9 +257,15 @@ pub unsafe extern "C" fn insn_in_hook_proxy<D, F>(
 where
     F: FnMut(&mut crate::Unicorn<D>, u32, usize) -> u32,
 {
+    if user_data.is_null() {
+        return 0;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return 0;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc, port, size)
@@ -236,9 +278,15 @@ pub unsafe extern "C" fn insn_invalid_hook_proxy<D, F>(
 where
     F: FnMut(&mut crate::Unicorn<D>) -> bool,
 {
+    if user_data.is_null() {
+        return false;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return false;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc)
@@ -253,9 +301,15 @@ pub unsafe extern "C" fn insn_out_hook_proxy<D, F>(
 ) where
     F: FnMut(&mut crate::Unicorn<D>, u32, usize, u32),
 {
+    if user_data.is_null() {
+        return;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc, port, size, value);
@@ -265,9 +319,15 @@ pub unsafe extern "C" fn insn_sys_hook_proxy<D, F>(uc: uc_handle, user_data: *mu
 where
     F: FnMut(&mut crate::Unicorn<D>),
 {
+    if user_data.is_null() {
+        return;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     (user_data.callback)(&mut user_data_uc);
@@ -283,9 +343,15 @@ pub unsafe extern "C" fn tlb_lookup_hook_proxy<D, F>(
 where
     F: FnMut(&mut crate::Unicorn<D>, u64, MemType) -> Option<TlbEntry>,
 {
+    if user_data.is_null() {
+        return false;
+    }
     let user_data = &mut *user_data;
+    let Some(inner) = user_data.uc.upgrade() else {
+        return false;
+    };
     let mut user_data_uc = Unicorn {
-        inner: user_data.uc.upgrade().unwrap(),
+        inner,
     };
     debug_assert_eq!(uc, user_data_uc.get_handle());
     let r = (user_data.callback)(&mut user_data_uc, vaddr, mem_type);