diff --git a/croaring/src/bitmap64/imp.rs b/croaring/src/bitmap64/imp.rs
index d9b139d..aba3fdf 100644
--- a/croaring/src/bitmap64/imp.rs
+++ b/croaring/src/bitmap64/imp.rs
@@ -696,6 +696,7 @@ impl Bitmap64 {
     /// assert_eq!(first_over_50, ControlFlow::Break(100));
     /// ```
     // TODO: If we can do external iteration, this function is unnecessary
+    // TODO: Panic safety?!
     #[inline]
     pub fn for_each<F, O>(&self, f: F) -> ControlFlow<O>
     where
diff --git a/fuzz/Cargo.toml b/fuzz/Cargo.toml
index 8532d7a..56e9e7e 100644
--- a/fuzz/Cargo.toml
+++ b/fuzz/Cargo.toml
@@ -27,6 +27,12 @@ path = "fuzz_targets/fuzz_ops.rs"
 test = false
 doc = false
 
+[[bin]]
+name = "fuzz_ops64"
+path = "fuzz_targets/fuzz_ops64.rs"
+test = false
+doc = false
+
 [[bin]]
 name = "against_bitvec"
 path = "fuzz_targets/against_bitvec.rs"
diff --git a/fuzz/fuzz_targets/arbitrary_ops64/mod.rs b/fuzz/fuzz_targets/arbitrary_ops64/mod.rs
new file mode 100644
index 0000000..0809a93
--- /dev/null
+++ b/fuzz/fuzz_targets/arbitrary_ops64/mod.rs
@@ -0,0 +1,292 @@
+use croaring::{Bitmap64, Treemap};
+use libfuzzer_sys::arbitrary::{self, Arbitrary, Unstructured};
+use std::mem;
+use std::ops::RangeInclusive;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
+#[repr(transparent)]
+pub struct Num(pub u64);
+
+pub const MAX_NUM: u64 = 0x1_0000 * 260;
+
+impl<'a> Arbitrary<'a> for Num {
+    fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
+        Ok(Self(u.int_in_range(0..=(MAX_NUM - 1))?))
+    }
+}
+
+#[derive(Arbitrary, Debug)]
+pub enum MutableBitmapOperation {
+    Add(Num),
+    AddChecked(Num),
+    AddMany(Vec<Num>),
+    AddRange(RangeInclusive<Num>),
+    RemoveRange(RangeInclusive<Num>),
+    Copy,
+    Clear,
+    Remove(Num),
+    RemoveChecked(Num),
+    RunOptimize,
+    RemoveRunCompression,
+    // Add to the max key (or with 0xFFFFFFFF_FFFF0000)
+    AddToMax(u16),
+}
+
+#[derive(Arbitrary, Debug)]
+pub enum ReadBitmapOp {
+    ContainsRange(RangeInclusive<Num>),
+    Contains(Num),
+    RangeCardinality(RangeInclusive<Num>),
+    Cardinality,
+    Flip(RangeInclusive<Num>),
+    ToVec,
+    GetPortableSerializedSizeInBytes,
+    GetNativeSerializedSizeInBytes,
+    GetFrozenSerializedSizeInBytes,
+    IsEmpty,
+    AddOffset(i64),
+    IntersectWithRange(RangeInclusive<Num>),
+    Minimum,
+    Maximum,
+    Rank(Num),
+    Index(Num),
+    Select(Num),
+    Statistics,
+    Clone,
+    Debug,
+    WithIter(Vec<IterOperation>),
+}
+
+#[derive(Arbitrary, Debug)]
+pub enum BitmapCompOperation {
+    Eq,
+    IsSubset,
+    IsStrictSubset,
+    Intersect,
+    JacardIndex,
+    And,
+    Or,
+    Xor,
+    AndNot,
+}
+
+#[derive(Arbitrary, Debug)]
+pub enum IterOperation {
+    ResetAtOrAfter(u64),
+    ReadNext,
+    NextMany(u16),
+}
+
+impl MutableBitmapOperation {
+    pub fn on_treemap(&self, b: &mut Treemap) {
+        match *self {
+            MutableBitmapOperation::Add(Num(i)) => {
+                b.add(i);
+            }
+            MutableBitmapOperation::AddChecked(Num(i)) => {
+                let expected = !b.contains(i);
+                let result = b.add_checked(i);
+                assert_eq!(expected, result);
+            }
+            MutableBitmapOperation::AddMany(ref items) => {
+                for &Num(item) in items {
+                    b.add(item)
+                }
+            }
+            MutableBitmapOperation::AddRange(ref r) => {
+                b.add_range(r.start().0..=r.end().0);
+            }
+            MutableBitmapOperation::RemoveRange(ref r) => {
+                b.remove_range(r.start().0..=r.end().0);
+            }
+            MutableBitmapOperation::Clear => {
+                b.clear();
+            }
+            MutableBitmapOperation::Remove(Num(i)) => {
+                b.remove(i);
+            }
+            MutableBitmapOperation::RemoveChecked(Num(i)) => {
+                let expected = b.contains(i);
+                let result = b.remove_checked(i);
+                assert_eq!(expected, result);
+            }
+            MutableBitmapOperation::RunOptimize => {
+                b.run_optimize();
+            }
+            MutableBitmapOperation::RemoveRunCompression => {
+                b.remove_run_compression();
+            }
+            MutableBitmapOperation::Copy => {
+                *b = b.clone();
+            }
+            MutableBitmapOperation::AddToMax(low_bits) => {
+                const UPPER_BITS: u64 = 0xFFFF_FFFF_FFFF_0000;
+                b.add(UPPER_BITS | u64::from(low_bits));
+            }
+        }
+    }
+
+    pub fn on_bitmap64(&self, b: &mut Bitmap64) {
+        match *self {
+            MutableBitmapOperation::Add(Num(i)) => {
+                b.add(i);
+            }
+            MutableBitmapOperation::AddChecked(Num(i)) => {
+                let expected = !b.contains(i);
+                let result = b.add_checked(i);
+                assert_eq!(expected, result);
+            }
+            MutableBitmapOperation::AddMany(ref items) => {
+                let items: &[u64] = unsafe { mem::transmute(&items[..]) };
+                b.add_many(items);
+            }
+            MutableBitmapOperation::AddRange(ref range) => {
+                b.add_range(range.start().0..=range.end().0);
+            }
+            MutableBitmapOperation::RemoveRange(ref range) => {
+                b.remove_range(range.start().0..=range.end().0);
+            }
+            MutableBitmapOperation::Copy => {
+                *b = b.clone();
+            }
+            MutableBitmapOperation::Clear => {
+                if !b.is_empty() {
+                    b.remove_range(b.minimum().unwrap()..=b.maximum().unwrap())
+                }
+            },
+            MutableBitmapOperation::Remove(Num(i)) => {
+                b.remove(i);
+            }
+            MutableBitmapOperation::RemoveChecked(Num(i)) => {
+                let expected = b.contains(i);
+                let result = b.remove_checked(i);
+                assert_eq!(expected, result);
+            }
+            MutableBitmapOperation::RunOptimize => {
+                b.run_optimize();
+            }
+            MutableBitmapOperation::RemoveRunCompression => {
+                // Unsupported
+            }
+            MutableBitmapOperation::AddToMax(low_bits) => {
+                const UPPER_BITS: u64 = 0xFFFF_FFFF_FFFF_0000;
+                b.add(UPPER_BITS | u64::from(low_bits));
+            }
+        }
+    }
+}
+
+impl BitmapCompOperation {
+    pub fn on_treemap(&self, lhs: &mut Treemap, rhs: &Treemap) {
+        match *self {
+            BitmapCompOperation::Eq => {
+                _ = lhs == rhs;
+                assert_eq!(lhs, lhs);
+            }
+            BitmapCompOperation::IsSubset => {
+                _ = lhs.is_subset(rhs);
+                assert!(lhs.is_subset(lhs));
+            }
+            BitmapCompOperation::IsStrictSubset => {
+                lhs.is_strict_subset(rhs);
+                assert!(!lhs.is_strict_subset(lhs));
+            }
+            BitmapCompOperation::Intersect => {
+                // Unimplemented
+            }
+            BitmapCompOperation::JacardIndex => {
+                // Unimplemented
+            }
+            BitmapCompOperation::And => {
+                assert_eq!(lhs.and(lhs), *lhs);
+
+                let res = lhs.and(rhs);
+                lhs.and_inplace(rhs);
+                assert_eq!(*lhs, res);
+            }
+            BitmapCompOperation::Or => {
+                assert_eq!(lhs.or(lhs), *lhs);
+
+                let res = lhs.or(rhs);
+
+                lhs.or_inplace(rhs);
+                assert_eq!(*lhs, res);
+            }
+            BitmapCompOperation::Xor => {
+                assert!(lhs.xor(lhs).is_empty());
+
+                let res = lhs.xor(rhs);
+
+                lhs.xor_inplace(rhs);
+                assert_eq!(*lhs, res);
+            }
+            BitmapCompOperation::AndNot => {
+                assert!(lhs.andnot(lhs).is_empty());
+
+                let res = lhs.andnot(rhs);
+
+                lhs.andnot_inplace(rhs);
+                assert_eq!(*lhs, res);
+            }
+        }
+    }
+    pub fn on_roaring64(&self, lhs: &mut Bitmap64, rhs: &Bitmap64) {
+        match *self {
+            BitmapCompOperation::Eq => {
+                _ = lhs == rhs;
+                assert_eq!(lhs, lhs);
+            }
+            BitmapCompOperation::IsSubset => {
+                _ = lhs.is_subset(rhs);
+                assert!(lhs.is_subset(lhs));
+            }
+            BitmapCompOperation::IsStrictSubset => {
+                lhs.is_strict_subset(rhs);
+                assert!(!lhs.is_strict_subset(lhs));
+            }
+            BitmapCompOperation::Intersect => {
+                _ = lhs.intersect(rhs);
+                assert!(lhs.is_empty() || lhs.intersect(lhs));
+            }
+            BitmapCompOperation::JacardIndex => {
+                _ = lhs.jaccard_index(rhs);
+                _ = lhs.jaccard_index(lhs);
+            }
+            BitmapCompOperation::And => {
+                assert_eq!(lhs.and(lhs), *lhs);
+
+                let res = lhs.and(rhs);
+                assert_eq!(res.cardinality(), lhs.and_cardinality(rhs));
+                lhs.and_inplace(rhs);
+                assert_eq!(*lhs, res);
+            }
+            BitmapCompOperation::Or => {
+                assert_eq!(lhs.or(lhs), *lhs);
+
+                let res = lhs.or(rhs);
+                assert_eq!(res.cardinality(), lhs.or_cardinality(rhs));
+
+                lhs.or_inplace(rhs);
+                assert_eq!(*lhs, res);
+            }
+            BitmapCompOperation::Xor => {
+                assert!(lhs.xor(lhs).is_empty());
+
+                let res = lhs.xor(rhs);
+                assert_eq!(res.cardinality(), lhs.xor_cardinality(rhs));
+
+                lhs.xor_inplace(rhs);
+                assert_eq!(*lhs, res);
+            }
+            BitmapCompOperation::AndNot => {
+                assert!(lhs.andnot(lhs).is_empty());
+
+                let res = lhs.andnot(rhs);
+                assert_eq!(res.cardinality(), lhs.andnot_cardinality(rhs));
+
+                lhs.andnot_inplace(rhs);
+                assert_eq!(*lhs, res);
+            }
+        }
+    }
+}
diff --git a/fuzz/fuzz_targets/fuzz_ops64.rs b/fuzz/fuzz_targets/fuzz_ops64.rs
new file mode 100644
index 0000000..2007afe
--- /dev/null
+++ b/fuzz/fuzz_targets/fuzz_ops64.rs
@@ -0,0 +1,52 @@
+#![no_main]
+
+use crate::arbitrary_ops64::*;
+use croaring::{Bitmap64, Treemap};
+use libfuzzer_sys::arbitrary;
+use libfuzzer_sys::arbitrary::Arbitrary;
+use libfuzzer_sys::fuzz_target;
+use std::ops::ControlFlow;
+
+mod arbitrary_ops64;
+
+fuzz_target!(|input: FuzzInput| {
+    let mut lhs64 = Bitmap64::new();
+    let mut rhs64 = Bitmap64::new();
+    let mut lhs_tree = Treemap::new();
+    let mut rhs_tree = Treemap::new();
+
+    for op in &input.lhs_ops {
+        op.on_bitmap64(&mut lhs64);
+        op.on_treemap(&mut lhs_tree);
+    }
+    for op in &input.rhs_ops {
+        op.on_bitmap64(&mut rhs64);
+        op.on_treemap(&mut rhs_tree);
+    }
+
+    for op in &input.comp_ops {
+        op.on_roaring64(&mut lhs64, &rhs64);
+        op.on_treemap(&mut lhs_tree, &rhs_tree);
+    }
+
+    assert_64_eq(&lhs64, &lhs_tree);
+    assert_64_eq(&rhs64, &rhs_tree);
+});
+
+#[derive(Arbitrary, Debug)]
+struct FuzzInput {
+    lhs_ops: Vec<MutableBitmapOperation>,
+    rhs_ops: Vec<MutableBitmapOperation>,
+    comp_ops: Vec<BitmapCompOperation>,
+    // view_ops: Vec<ReadBitmapOp>,
+}
+
+fn assert_64_eq(lhs: &Bitmap64, rhs: &Treemap) {
+    assert_eq!(lhs.cardinality(), rhs.cardinality());
+    let mut rhs_iter = rhs.iter();
+    let res = lhs.for_each(|v| -> ControlFlow<()> {
+        assert_eq!(rhs_iter.next(), Some(v));
+        ControlFlow::Continue(())
+    });
+    assert_eq!(res, ControlFlow::Continue(()));
+}