diff --git a/fuzz/fuzz.rs b/fuzz/fuzz.rs
index 801068e..4b52a0b 100644
--- a/fuzz/fuzz.rs
+++ b/fuzz/fuzz.rs
@@ -1,18 +1,21 @@
 #![no_main]
 use libfuzzer_sys::fuzz_target;
-use std::collections::VecDeque;
 use std::collections::HashMap;
 
 extern crate add_ed;
 use add_ed::io::fake_io::FakeIO;
 
-fuzz_target!(|data: VecDeque<String>| {
+// You can do anything in 4 input lines, so that should be enough
+// (and it should help with the out-of-memory problems while fuzzing)
+fuzz_target!(|data: [String; 4]| {
   let mut ui = add_ed::ui::ScriptedUI {
-    input: data,
+    input: data.into(),
     print_ui: None,
   };
   let mut io = FakeIO{fake_fs: HashMap::new(), fake_shell: HashMap::new()};
-  let mut buffer = add_ed::buffer::Buffer::new();
-  let mut ed = add_ed::Ed::new(&mut buffer, &mut io, "".to_string());
-  let _ = ed.run_macro(&mut ui);
+  let macro_store = HashMap::new();
+  let mut ed = add_ed::Ed::new(&mut io, &macro_store);
+  loop {
+    if let Ok(true) = ed.get_and_run_command(&mut ui) { break; }
+  }
 });
diff --git a/src/cmd/parsing/selection.rs b/src/cmd/parsing/selection.rs
index 5d196ab..32c9dd4 100644
--- a/src/cmd/parsing/selection.rs
+++ b/src/cmd/parsing/selection.rs
@@ -54,14 +54,11 @@ pub fn parse_index(
               // then an offset. Not caught earlier so we can give a more
               // detailed error. Same error logic as post loop State::Default
               if let Some(_) = current_ind {return Err(
+                // Note that this reports getting digits after another index.
+                // We catch it here to get all the digits before erroring.
                 EdError::IndicesUnrelated{
-                  prior_index: input[start..i].to_owned(),
-                  // Find the end of the current index
-                  unrelated_index: input[i..]
-                      .find(|c: char| !c.is_ascii_digit())
-                      .map(|end| &input[i..end] )
-                      .unwrap_or(&input[i..])
-                      .to_owned(),
+                  prior_index: input[..start].to_owned(),
+                  unrelated_index: input[start..i].to_owned(),
                 }
               )}
               // If there is numeric input before, handle that
@@ -121,8 +118,17 @@ pub fn parse_index(
       State::Tag => {
         if let Some(_) = current_ind { return Err(
           EdError::IndicesUnrelated{
+            // Safe, as the -1 is to exclude the ' (which is 1 byte long)
             prior_index: input[..i-1].to_owned(),
-            unrelated_index: input[i-1..i+1].to_owned(),
+            // As the start -1 includes the ' the start is safe, but we can't
+            // assume the given tag is 1 byte long.
+            unrelated_index: {
+              let mut index = String::new();
+              for ch in input[i-1..].chars().take(2) {
+                index.push(ch);
+              }
+              index
+            },
           }
         )}
         current_ind = Some(Ind::Tag(ch));
@@ -304,7 +310,7 @@ pub fn interpret_index(
     // These are relative to the prior, so have no indexing per-se
     Ind::Add(inner, offset) => {
       let inner = interpret_index(state, *inner, old_selection)?;
-      Ok(inner+offset)
+      Ok(inner.saturating_add(offset))
     },
     Ind::Sub(inner, offset) => {
       let inner = interpret_index(state, *inner, old_selection)?;
diff --git a/src/error/display.rs b/src/error/display.rs
index c89c047..6bc64b6 100644
--- a/src/error/display.rs
+++ b/src/error/display.rs
@@ -110,7 +110,7 @@ impl std::fmt::Display for EdError {
         text,
       ),
       IndicesUnrelated{prior_index, unrelated_index} => write!(f,
-        "Received index `{}` immediately after index `{}`.",
+        "Received non-chainable index `{}` immediately after index `{}`.",
         unrelated_index,
         prior_index,
       ),
diff --git a/tests/old_fuss_fails.rs b/tests/old_fuss_fails.rs
new file mode 100644
index 0000000..85ef96b
--- /dev/null
+++ b/tests/old_fuss_fails.rs
@@ -0,0 +1,29 @@
+mod shared;
+use shared::fixtures::{
+  ErrorTest,
+};
+use add_ed::EdError;
+
+#[test]
+fn unrelated_indice_with_unicode_tag() {
+  ErrorTest{
+    init_buffer: vec![],
+    command_input: vec!["'''🏷 G"],
+    expected_error: EdError::IndicesUnrelated{
+      prior_index: "''".to_owned(),
+      unrelated_index: "'🏷".to_owned(),
+    },
+  }.run()
+}
+
+#[test]
+fn index_overflow() {
+  ErrorTest{
+    init_buffer: vec![],
+    command_input: vec!["9999999999999999999+9999999999999999999"],
+    expected_error: EdError::IndexTooBig{
+      index: 18_446_744_073_709_551_615,
+      buffer_len: 0,
+    },
+  }.run()
+}
diff --git a/tests/shared/inner_fixture.rs b/tests/shared/inner_fixture.rs
index 38610ae..5d8ecb3 100644
--- a/tests/shared/inner_fixture.rs
+++ b/tests/shared/inner_fixture.rs
@@ -3,7 +3,7 @@
 use std::collections::HashMap;
 
 use super::{
-  dummy_io::DummyIO,
+  fake_io::FakeIO,
   mock_ui::{Print, MockUI},
 };
 use add_ed::{
@@ -33,7 +33,10 @@ pub fn inner_fixture(
   expected_prints: Vec<Print>,
 ) {
   // Instantiate dummy IO
-  let mut io = DummyIO::new();
+  let mut io = FakeIO{
+    fake_fs: HashMap::new(),
+    fake_shell: HashMap::new(),
+  };
   // Apply given or default to no macros
   let macros = init_macros.unwrap_or(HashMap::new());
   // Create ed state and init ed.buffer