diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index 79d1ccf637d37..622cc68964bf7 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -2008,10 +2008,10 @@ impl From<Box<str>> for String {
     }
 }
 
-#[stable(feature = "box_from_str", since = "1.18.0")]
-impl Into<Box<str>> for String {
-    fn into(self) -> Box<str> {
-        self.into_boxed_str()
+#[stable(feature = "box_from_str", since = "1.20.0")]
+impl From<String> for Box<str> {
+    fn from(s: String) -> Box<str> {
+        s.into_boxed_str()
     }
 }
 
diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index 1a91417ca0e92..5f0b11a616eb0 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -585,11 +585,11 @@ impl From<Box<CStr>> for CString {
     }
 }
 
-#[stable(feature = "box_from_c_string", since = "1.18.0")]
-impl Into<Box<CStr>> for CString {
+#[stable(feature = "box_from_c_string", since = "1.20.0")]
+impl From<CString> for Box<CStr> {
     #[inline]
-    fn into(self) -> Box<CStr> {
-        self.into_boxed_c_str()
+    fn from(s: CString) -> Box<CStr> {
+        s.into_boxed_c_str()
     }
 }
 
diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index 42d641706a894..02a13ed7a5a03 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -540,10 +540,10 @@ impl From<Box<OsStr>> for OsString {
     }
 }
 
-#[stable(feature = "box_from_os_string", since = "1.18.0")]
-impl Into<Box<OsStr>> for OsString {
-    fn into(self) -> Box<OsStr> {
-        self.into_boxed_os_str()
+#[stable(feature = "box_from_os_string", since = "1.20.0")]
+impl From<OsString> for Box<OsStr> {
+    fn from(s: OsString) -> Box<OsStr> {
+        s.into_boxed_os_str()
     }
 }
 
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index 472ce6bc4fe9e..e7c7be981d25f 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -1348,10 +1348,10 @@ impl From<Box<Path>> for PathBuf {
     }
 }
 
-#[stable(feature = "box_from_path_buf", since = "1.18.0")]
-impl Into<Box<Path>> for PathBuf {
-    fn into(self) -> Box<Path> {
-        self.into_boxed_path()
+#[stable(feature = "box_from_path_buf", since = "1.20.0")]
+impl From<PathBuf> for Box<Path> {
+    fn from(p: PathBuf) -> Box<Path> {
+        p.into_boxed_path()
     }
 }