diff --git a/src/ast.rs b/src/ast.rs
index ae036c2..e782df2 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -2,8 +2,11 @@ use std::borrow::Cow;
 use std::fmt;
 
 use chrono::{DateTime, FixedOffset};
+use nom_locate::LocatedSpan;
 
-use crate::parser::{parse_multiple_patches, parse_single_patch, ParseError};
+use crate::parser::{
+    parse_multiple_patches, parse_single_patch, parse_single_patch_with_remaining, ParseError,
+};
 
 /// A complete patch summarizing the differences between two files
 #[derive(Debug, Clone, Eq, PartialEq)]
@@ -82,6 +85,12 @@ impl<'a> Patch<'a> {
         parse_single_patch(s)
     }
 
+    pub fn from_single_with_remaining(
+        s: &'a str,
+    ) -> Result<(Self, Option<LocatedSpan<&'a str>>), ParseError<'a>> {
+        parse_single_patch_with_remaining(s)
+    }
+
     /// Attempt to parse as many patches as possible from the given string. This is useful for when
     /// you have a complete diff of many files.
     ///
diff --git a/src/parser.rs b/src/parser.rs
index 2ca42c7..a16e38f 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -12,6 +12,7 @@ use nom::{
     multi::{many0, many1},
     sequence::{delimited, preceded, terminated, tuple},
 };
+use nom_locate::LocatedSpan;
 
 use crate::ast::*;
 
@@ -75,16 +76,27 @@ fn consume_content_line(input: Input<'_>) -> IResult<Input<'_>, (&str, bool)> {
 
 pub(crate) fn parse_single_patch(s: &str) -> Result<Patch<'_>, ParseError<'_>> {
     let (remaining_input, patch) = patch(Input::new(s))?;
-    // Parser should return an error instead of producing remaining input
-    assert!(
-        remaining_input.fragment().is_empty(),
-        "bug: failed to parse entire input. \
-        Remaining: '{}'",
-        remaining_input.fragment()
-    );
+    if !remaining_input.fragment().is_empty() {
+        return Err(ParseError {
+            line: remaining_input.location_line(),
+            offset: 0,
+            fragment: remaining_input.fragment(),
+            kind: nom::error::ErrorKind::Fail,
+        });
+    }
     Ok(patch)
 }
 
+pub(crate) fn parse_single_patch_with_remaining(
+    s: &str,
+) -> Result<(Patch<'_>, Option<LocatedSpan<&str>>), ParseError<'_>> {
+    let (remaining_input, patch) = patch(Input::new(s))?;
+    if remaining_input.fragment().is_empty() {
+        return Ok((patch, None));
+    }
+    Ok((patch, Some(remaining_input)))
+}
+
 pub(crate) fn parse_multiple_patches(s: &str) -> Result<Vec<Patch<'_>>, ParseError<'_>> {
     let (remaining_input, patches) = multiple_patches(Input::new(s))?;
     debug_assert!(