diff --git a/src/path/pathbuf.rs b/src/path/pathbuf.rs
index 808acb2e..e684df89 100644
--- a/src/path/pathbuf.rs
+++ b/src/path/pathbuf.rs
@@ -327,6 +327,8 @@ impl<P: AsRef<Path>> stream::Extend<P> for PathBuf {
         let stream = stream.into_stream();
 
         Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
             while let Some(item) = stream.next().await {
                 self.push(item.as_ref());
             }
diff --git a/src/stream/from_fn.rs b/src/stream/from_fn.rs
index 3ace6583..8067176e 100644
--- a/src/stream/from_fn.rs
+++ b/src/stream/from_fn.rs
@@ -30,7 +30,7 @@ impl<F> Unpin for FromFn<F> {}
 /// use async_std::stream;
 ///
 /// let mut count = 0u8;
-/// let mut s = stream::from_fn(|| {
+/// let s = stream::from_fn(|| {
 ///     count += 1;
 ///     if count > 3 {
 ///         None
@@ -39,6 +39,8 @@ impl<F> Unpin for FromFn<F> {}
 ///     }
 /// });
 ///
+/// pin_utils::pin_mut!(s);
+///
 /// assert_eq!(s.next().await, Some(1));
 /// assert_eq!(s.next().await, Some(2));
 /// assert_eq!(s.next().await, Some(3));
diff --git a/src/stream/repeat_with.rs b/src/stream/repeat_with.rs
index 954693d8..e183a77c 100644
--- a/src/stream/repeat_with.rs
+++ b/src/stream/repeat_with.rs
@@ -28,7 +28,9 @@ impl<F> Unpin for RepeatWith<F> {}
 /// use async_std::prelude::*;
 /// use async_std::stream;
 ///
-/// let mut s = stream::repeat_with(|| 1);
+/// let s = stream::repeat_with(|| 1);
+///
+/// pin_utils::pin_mut!(s);
 ///
 /// assert_eq!(s.next().await, Some(1));
 /// assert_eq!(s.next().await, Some(1));
diff --git a/src/string/extend.rs b/src/string/extend.rs
index 43bd46d6..55bec0c5 100644
--- a/src/string/extend.rs
+++ b/src/string/extend.rs
@@ -13,6 +13,8 @@ impl stream::Extend<char> for String {
         self.reserve(stream.size_hint().0);
 
         Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
             while let Some(item) = stream.next().await {
                 self.push(item);
             }
@@ -28,6 +30,8 @@ impl<'b> stream::Extend<&'b char> for String {
         let stream = stream.into_stream();
 
         Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
             while let Some(item) = stream.next().await {
                 self.push(*item);
             }
@@ -43,6 +47,8 @@ impl<'b> stream::Extend<&'b str> for String {
         let stream = stream.into_stream();
 
         Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
             while let Some(item) = stream.next().await {
                 self.push_str(item);
             }
@@ -58,6 +64,8 @@ impl stream::Extend<String> for String {
         let stream = stream.into_stream();
 
         Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
             while let Some(item) = stream.next().await {
                 self.push_str(&item);
             }
@@ -73,6 +81,8 @@ impl<'b> stream::Extend<Cow<'b, str>> for String {
         let stream = stream.into_stream();
 
         Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
             while let Some(item) = stream.next().await {
                 self.push_str(&item);
             }
diff --git a/src/unit/extend.rs b/src/unit/extend.rs
index 5b0bc1d1..55c8e0d0 100644
--- a/src/unit/extend.rs
+++ b/src/unit/extend.rs
@@ -11,6 +11,8 @@ impl stream::Extend<()> for () {
         let stream = stream.into_stream();
 
         Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
             while let Some(_) = stream.next().await {}
         })
     }