diff --git a/Cargo.toml b/Cargo.toml
index 707025a..73d8ec3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,7 +22,7 @@ version = "0.1.36"
 default-features = false
 
 [dependencies.nom]
-version = "6"
+version = "7.0.0"
 default-features = false
 
 [dependencies.chrono]
diff --git a/src/common.rs b/src/common.rs
index 225b430..1df8aa6 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -96,7 +96,7 @@ pub fn take_n_digits(n: usize) -> impl FnMut(&str) -> StrResult<&str> {
 pub fn two_digits<T: FromStr>(remain: &str) -> StrResult<T> {
     let (remain, two) = take_n_digits(2)(remain)?;
     // NonZeroU8's FromStr implementation rejects 00.
-    let (_, parsed) = nom::parse_to!(two, T)?;
+    let parsed = two.parse_to_err()?;
     Ok((remain, parsed))
 }
 
@@ -104,7 +104,7 @@ pub fn two_digits<T: FromStr>(remain: &str) -> StrResult<T> {
 pub fn two_digits_zero_none(remain: &str) -> StrResult<Option<NonZeroU8>> {
     let (remain, two) = take_n_digits(2).parse(remain)?;
     // NonZeroU8's FromStr implementation rejects 00.
-    let (_, parsed) = nom::parse_to!(two, u8)?;
+    let parsed = two.parse_to_err()?;
     Ok((remain, NonZeroU8::new(parsed)))
 }
 
@@ -124,10 +124,29 @@ pub enum UnvalidatedTz {
     HoursMinutes { positive: bool, hh: u8, mm: u8 },
 }
 
+pub(crate) trait ParseToExt<R>: ParseTo<R>
+where
+    R: FromStr,
+{
+    fn parse_to_err(self) -> Result<R, nom::Err<nom::error::Error<Self>>>
+    where
+        Self: Sized,
+    {
+        self.parse_to().ok_or_else(|| {
+            nom::Err::Error(NomParseError::from_error_kind(
+                self,
+                // whatever. nom should have an Other errorkind.
+                nom::error::ErrorKind::MapRes,
+            ))
+        })
+    }
+}
+impl<S: ParseTo<R>, R: FromStr> ParseToExt<R> for S {}
+
 pub fn year_n(n: usize) -> impl FnMut(&str) -> StrResult<i32> {
     move |remain| {
         let (remain, four) = take_n_digits(n)(remain)?;
-        let (_, parsed) = nom::parse_to!(four, i32)?;
+        let parsed: i32 = four.parse_to_err()?;
         Ok((remain, parsed))
     }
 }
@@ -136,7 +155,7 @@ pub fn year_n_signed(n: usize) -> impl FnMut(&str) -> StrResult<i32> {
     move |remain| {
         let (remain, sign) = minus_sign(-1i32, 1)(remain)?;
         let (remain, four) = take_n_digits(n)(remain)?;
-        let (_, parsed) = nom::parse_to!(four, i32)?;
+        let parsed: i32 = four.parse_to_err()?;
         if sign == -1 && parsed == 0 {
             return Err(nom::Err::Error(NomParseError::from_error_kind(
                 remain,
@@ -153,7 +172,7 @@ pub fn signed_year_min_n(n: usize) -> impl FnMut(&str) -> StrResult<i64> {
         let nonzero_digit = ncc::satisfy(|c| c.is_ascii_digit() && c != '0');
         let (remain, sign) = minus_sign(-1i64, 1i64).parse(remain)?;
         let (remain, digs) = nc::recognize(nonzero_digit.and(take_min_n_digits(n - 1)))(remain)?;
-        let (_, parsed) = nom::parse_to!(digs, i64)?;
+        let parsed: i64 = digs.parse_to_err()?;
         Ok((remain, parsed * sign))
     }
 }
diff --git a/src/level0/parser.rs b/src/level0/parser.rs
index a2c5871..565a938 100644
--- a/src/level0/parser.rs
+++ b/src/level0/parser.rs
@@ -4,8 +4,8 @@
 //
 // Copyright © 2021 Corporation for Digital Scholarship
 
-use crate::helpers::ParserExt;
 use crate::ParseError;
+use crate::{common::ParseToExt, helpers::ParserExt};
 
 #[allow(unused_imports)]
 use nom::{
@@ -78,7 +78,7 @@ pub(crate) fn date(remain: &str) -> StrResult<Date> {
 /// Level 0 year only, so simply exactly four digits 0-9. That's it.
 fn year4(remain: &str) -> StrResult<i32> {
     let (remain, four) = take_n_digits(4)(remain)?;
-    let (_, parsed) = nom::parse_to!(four, i32)?;
+    let parsed = four.parse_to_err()?;
     Ok((remain, parsed))
 }
 
diff --git a/src/level2/parser.rs b/src/level2/parser.rs
index 8cc03ed..63c56fa 100644
--- a/src/level2/parser.rs
+++ b/src/level2/parser.rs
@@ -12,7 +12,7 @@ use nom::{
 };
 
 use crate::{
-    common::{signed_year_min_n, year_n_signed, StrResult},
+    common::{signed_year_min_n, year_n_signed, ParseToExt, StrResult},
     helpers::ParserExt,
     ParseError,
 };
@@ -80,14 +80,8 @@ fn scientific_y(remain: &str) -> StrResult<ScientificYear> {
         .or(ns::preceded(ncc::char('Y'), signed_year_min_n(5)).map(|y| (y, None)))
         .and(ns::preceded(s, ncc::digit1).optional())
         .parse(remain)?;
-    let exponent = opt_e
-        .map(|e| nom::parse_to!(e, u16))
-        .transpose()?
-        .map(|x| x.1);
-    let sig_digits = opt_s
-        .map(|s| nom::parse_to!(s, u16))
-        .transpose()?
-        .map(|x| x.1);
+    let exponent = opt_e.map(ParseToExt::<u16>::parse_to_err).transpose()?;
+    let sig_digits = opt_s.map(ParseToExt::<u16>::parse_to_err).transpose()?;
     Ok((
         remain,
         ScientificYear {
@@ -103,7 +97,7 @@ fn scientific_4digit(remain: &str) -> StrResult<ScientificYear> {
     let (remain, (year, sd)) = year_n_signed(4)
         .and(ns::preceded(s, ncc::digit1))
         .parse(remain)?;
-    let (_, sd) = nom::parse_to!(sd, u16)?;
+    let sd: u16 = sd.parse_to_err()?;
     Ok((
         remain,
         ScientificYear {