diff --git a/src/method.rs b/src/method.rs
index b7b3b35..a795208 100644
--- a/src/method.rs
+++ b/src/method.rs
@@ -97,7 +96,7 @@ impl Method {
     pub const TRACE: Method = Method(Trace);
 
     /// Converts a slice of bytes to an HTTP method.
-    pub fn from_bytes(src: &[u8]) -> Result<Method, InvalidMethod> {
+    pub const fn from_bytes(src: &[u8]) -> Result<Method, InvalidMethod> {
         match src.len() {
             0 => Err(InvalidMethod::new()),
             3 => match src {
@@ -128,7 +127,10 @@ impl Method {
                 if src.len() < InlineExtension::MAX {
                     Method::extension_inline(src)
                 } else {
-                    let allocated = AllocatedExtension::new(src)?;
+                    let allocated = match AllocatedExtension::new(src) {
+                        Ok(a) => a,
+                        Err(e) => return Err(e),
+                    };
 
                     Ok(Method(ExtensionAllocated(allocated)))
                 }
@@ -136,8 +138,11 @@ impl Method {
         }
     }
 
-    fn extension_inline(src: &[u8]) -> Result<Method, InvalidMethod> {
-        let inline = InlineExtension::new(src)?;
+    const fn extension_inline(src: &[u8]) -> Result<Method, InvalidMethod> {
+        let inline = match InlineExtension::new(src) {
+            Ok(i) => i,
+            Err(err) => return Err(err),
+        };
 
         Ok(Method(ExtensionInline(inline)))
     }
@@ -288,7 +293,7 @@ impl FromStr for Method {
 }
 
 impl InvalidMethod {
-    fn new() -> InvalidMethod {
+    const fn new() -> InvalidMethod {
         InvalidMethod { _priv: () }
     }
 }
@@ -325,10 +330,12 @@ mod extension {
         // Method::from_bytes() assumes this is at least 7
         pub const MAX: usize = 15;
 
-        pub fn new(src: &[u8]) -> Result<InlineExtension, InvalidMethod> {
-            let mut data: [u8; InlineExtension::MAX] = Default::default();
+        pub const fn new(src: &[u8]) -> Result<InlineExtension, InvalidMethod> {
+            let mut data: [u8; InlineExtension::MAX] = [0; 15];
 
-            write_checked(src, &mut data)?;
+            if let Err(err) = write_checked(src, &mut data) {
+                return Err(err);
+            };
 
             // Invariant: write_checked ensures that the first src.len() bytes
             // of data are valid UTF-8.
@@ -339,15 +346,17 @@ mod extension {
             let InlineExtension(ref data, len) = self;
             // Safety: the invariant of InlineExtension ensures that the first
             // len bytes of data contain valid UTF-8.
-            unsafe {str::from_utf8_unchecked(&data[..*len as usize])}
+            unsafe { str::from_utf8_unchecked(&data[..*len as usize]) }
         }
     }
 
     impl AllocatedExtension {
-        pub fn new(src: &[u8]) -> Result<AllocatedExtension, InvalidMethod> {
+        pub const fn new(src: &[u8]) -> Result<AllocatedExtension, InvalidMethod> {
             let mut data: Vec<u8> = vec![0; src.len()];
 
-            write_checked(src, &mut data)?;
+            if let Err(err) = write_checked(src, &mut data) {
+                return Err(err);
+            };
 
             // Invariant: data is exactly src.len() long and write_checked
             // ensures that the first src.len() bytes of data are valid UTF-8.