diff --git a/lalrpop-test/src/lib.rs b/lalrpop-test/src/lib.rs
index 6696e83..ae0ab11 100644
--- a/lalrpop-test/src/lib.rs
+++ b/lalrpop-test/src/lib.rs
@@ -940,8 +940,9 @@ fn verify_lalrpop_generates_itself() {
 
     let actual = fs::read_to_string(grammar_file.with_extension("rs")).unwrap();
     let expected = fs::read_to_string(copied_grammar_file.with_extension("rs")).unwrap();
-    assert!(
-        actual == expected,
+    util::compare_str(
+        &actual,
+        &expected,
         "The snapshot does not match what lalrpop generates now.\n\
          Use ./snap.sh to generate a new snapshot of the lrgrammar",
     );
diff --git a/lalrpop-test/src/util/mod.rs b/lalrpop-test/src/util/mod.rs
index b7f73fc..7281c50 100644
--- a/lalrpop-test/src/util/mod.rs
+++ b/lalrpop-test/src/util/mod.rs
@@ -84,7 +84,15 @@ pub fn compare<D: Debug, E: Debug>(actual: D, expected: E) {
         let actual_s = format!("{:#?}", actual);
         let expected_s = format!("{:#?}", expected);
 
-        for diff in diff::lines(&actual_s, &expected_s) {
+        compare_str(&actual_s, &expected_s, "");
+    }
+}
+
+pub fn compare_str(actual: &str, expected: &str, msg: &str) {
+    if actual != expected {
+        let mut lines = 0;
+        for diff in diff::lines(actual, expected).into_iter().take(100) {
+            lines += 1;
             match diff {
                 diff::Result::Right(r) => println!("- {}", r),
                 diff::Result::Left(l) => println!("+ {}", l),
@@ -92,6 +100,9 @@ pub fn compare<D: Debug, E: Debug>(actual: D, expected: E) {
             }
         }
 
-        assert!(false);
+        if lines >= 100 {
+            println!("... more");
+        }
+        assert!(false, "{}", msg);
     }
 }