diff --git a/Cargo.lock b/Cargo.lock
index 91a54df..4ef8b80 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -300,6 +300,7 @@ dependencies = [
 name = "ppc750cl-fuzz"
 version = "0.2.0"
 dependencies = [
+ "clap",
  "num_cpus",
  "ppc750cl",
 ]
diff --git a/fuzz/Cargo.toml b/fuzz/Cargo.toml
index 5b846dc..138eca2 100644
--- a/fuzz/Cargo.toml
+++ b/fuzz/Cargo.toml
@@ -8,5 +8,6 @@ description = "Complete fuzzer for ppc750cl"
 repository = "https://github.com/terorie/ppc750cl"
 
 [dependencies]
+clap = "3"
 num_cpus = "1.13"
 ppc750cl = { path = "../disasm", version = "0.2.0" }
diff --git a/fuzz/src/main.rs b/fuzz/src/main.rs
index be0840b..ed0e5b5 100644
--- a/fuzz/src/main.rs
+++ b/fuzz/src/main.rs
@@ -1,5 +1,6 @@
 use std::io::Write;
 use std::ops::Range;
+use std::str::FromStr;
 use std::sync::atomic::{AtomicU32, Ordering};
 use std::sync::Arc;
 use std::time::{Duration, Instant};
@@ -8,8 +9,24 @@ use ppc750cl::formatter::FormattedIns;
 use ppc750cl::Ins;
 
 fn main() {
+    let matches = clap::Command::new("ppc750cl-fuzz")
+        .version("0.2.0")
+        .about("Complete \"fuzzer\" for ppc750cl disassembler")
+        .arg(
+            clap::Arg::new("threads")
+                .short('t')
+                .long("--threads")
+                .takes_value(true)
+                .help("Number of threads to use (default num CPUs)"),
+        )
+        .get_matches();
+
+    let threads = match matches.value_of("threads") {
+        Some(t) => u32::from_str(t).expect("invalid threads flag"),
+        None => num_cpus::get() as u32,
+    };
     let start = Instant::now();
-    let fuzzer = MultiFuzzer::new(num_cpus::get() as u32);
+    let fuzzer = MultiFuzzer::new(threads);
     fuzzer.run();
     println!("Finished in {:.2}s", start.elapsed().as_secs_f32());
 }
diff --git a/genisa/src/main.rs b/genisa/src/main.rs
index 8aad187..4591b9c 100644
--- a/genisa/src/main.rs
+++ b/genisa/src/main.rs
@@ -534,18 +534,13 @@ impl Isa {
         let use_match_arms = token_stream!(use_match_arms);
         let suffix_match_arms = token_stream!(suffix_match_arms);
         let simplified_ins_match_arms = token_stream!(simplified_ins_match_arms);
-        let field_accessors = self
-            .fields
-            .iter()
-            .map(|field| field.construct_accessor())
-            .collect::<Vec<_>>();
-        let field_accessors = token_stream!(field_accessors);
-        let modifier_accessors = self
-            .modifiers
-            .iter()
-            .map(|modifier| modifier.construct_accessor())
-            .collect::<Vec<_>>();
-        let modifier_accessors = token_stream!(modifier_accessors);
+        let field_accessors =
+            TokenStream::from_iter(self.fields.iter().map(|field| field.construct_accessor()));
+        let modifier_accessors = TokenStream::from_iter(
+            self.modifiers
+                .iter()
+                .map(|modifier| modifier.construct_accessor()),
+        );
         // Generate final fields function.
         let ins_impl = quote! {
             #[allow(clippy::all, unused_mut)]