diff --git a/onig/src/find.rs b/onig/src/find.rs
index b7be3ce5..b2fc046e 100644
--- a/onig/src/find.rs
+++ b/onig/src/find.rs
@@ -1,5 +1,5 @@
 use super::{Regex, Region, SearchOptions};
-use std::iter::Iterator;
+use std::iter::FusedIterator;
 
 impl Regex {
     /// Returns the capture groups corresponding to the leftmost-first match
@@ -299,8 +299,16 @@ impl<'t> Iterator for SubCaptures<'t> {
         let size = self.caps.len();
         (size, Some(size))
     }
+
+    fn count(self) -> usize {
+        self.caps.len()
+    }
 }
 
+impl<'t> FusedIterator for SubCaptures<'t> {}
+
+impl<'t> ExactSizeIterator for SubCaptures<'t> {}
+
 /// An iterator over capture group positions for a particular match of
 /// a regular expression.
 ///
@@ -327,8 +335,16 @@ impl<'t> Iterator for SubCapturesPos<'t> {
         let size = self.caps.len();
         (size, Some(size))
     }
+
+    fn count(self) -> usize {
+        self.caps.len()
+    }
 }
 
+impl<'t> FusedIterator for SubCapturesPos<'t> {}
+
+impl<'t> ExactSizeIterator for SubCapturesPos<'t> {}
+
 /// An iterator over all non-overlapping matches for a particular string.
 ///
 /// The iterator yields a tuple of integers corresponding to the start and end
@@ -380,6 +396,8 @@ impl<'r, 't> Iterator for FindMatches<'r, 't> {
     }
 }
 
+impl<'r, 't> FusedIterator for FindMatches<'r, 't> {}
+
 /// An iterator that yields all non-overlapping capture groups matching a
 /// particular regular expression.
 ///
@@ -433,6 +451,8 @@ impl<'r, 't> Iterator for FindCaptures<'r, 't> {
     }
 }
 
+impl<'r, 't> FusedIterator for FindCaptures<'r, 't> {}
+
 /// Yields all substrings delimited by a regular expression match.
 ///
 /// `'r` is the lifetime of the compiled expression and `'t` is the lifetime
@@ -466,6 +486,8 @@ impl<'r, 't> Iterator for RegexSplits<'r, 't> {
     }
 }
 
+impl<'r, 't> FusedIterator for RegexSplits<'r, 't> {}
+
 /// Yields at most `N` substrings delimited by a regular expression match.
 ///
 /// The last substring will be whatever remains after splitting.
@@ -498,6 +520,8 @@ impl<'r, 't> Iterator for RegexSplitsN<'r, 't> {
     }
 }
 
+impl<'r, 't> FusedIterator for RegexSplitsN<'r, 't> {}
+
 #[cfg(test)]
 mod tests {
     use super::super::*;
diff --git a/onig/src/region.rs b/onig/src/region.rs
index db653488..81cfe02d 100644
--- a/onig/src/region.rs
+++ b/onig/src/region.rs
@@ -1,6 +1,7 @@
 #![allow(clippy::transmute_ptr_to_ref)]
 
 use onig_sys;
+use std::iter::FusedIterator;
 use std::mem::transmute;
 use std::os::raw::{c_int, c_void};
 use std::ptr::null_mut;
@@ -252,6 +253,10 @@ impl<'a> Iterator for RegionIter<'a> {
     }
 }
 
+impl<'a> FusedIterator for RegionIter<'a> {}
+
+impl<'a> ExactSizeIterator for RegionIter<'a> {}
+
 #[cfg(test)]
 mod tests {
     use super::super::{Regex, SearchOptions};
diff --git a/onig/src/tree.rs b/onig/src/tree.rs
index f0216fd0..fa797564 100644
--- a/onig/src/tree.rs
+++ b/onig/src/tree.rs
@@ -1,7 +1,7 @@
 #![allow(clippy::transmute_ptr_to_ref)]
 
 use onig_sys;
-use std::iter::Iterator;
+use std::iter::FusedIterator;
 use std::mem::transmute;
 use std::ops::Index;
 
@@ -77,8 +77,16 @@ impl<'t> Iterator for CaptureTreeNodeIter<'t> {
         let size = self.node.len();
         (size, Some(size))
     }
+
+    fn count(self) -> usize {
+        self.node.len()
+    }
 }
 
+impl<'t> FusedIterator for CaptureTreeNodeIter<'t> {}
+
+impl<'t> ExactSizeIterator for CaptureTreeNodeIter<'t> {}
+
 #[cfg(test)]
 mod tests {
     use super::super::*;