diff --git a/cli/src/lib.rs b/cli/src/lib.rs
index 18d4e4de53..e6603cdbdb 100644
--- a/cli/src/lib.rs
+++ b/cli/src/lib.rs
@@ -35,6 +35,7 @@ pub const CMD_FORMAT: &str = "format";
 pub const FLAG_DEBUG: &str = "debug";
 pub const FLAG_DEV: &str = "dev";
 pub const FLAG_OPTIMIZE: &str = "optimize";
+pub const FLAG_MAX_THREADS: &str = "max-threads";
 pub const FLAG_OPT_SIZE: &str = "opt-size";
 pub const FLAG_LIB: &str = "lib";
 pub const FLAG_NO_LINK: &str = "no-link";
@@ -58,6 +59,14 @@ pub fn build_app<'a>() -> Command<'a> {
         .requires(ROC_FILE)
         .required(false);
 
+    let flag_max_threads = Arg::new(FLAG_MAX_THREADS)
+        .long(FLAG_MAX_THREADS)
+        .help("Limit the number of threads (and hence cores) used during compilation.")
+        .takes_value(true)
+        .requires(ROC_FILE)
+        .validator(|s| s.parse::<usize>())
+        .required(false);
+
     let flag_opt_size = Arg::new(FLAG_OPT_SIZE)
         .long(FLAG_OPT_SIZE)
         .help("Optimize the compiled program to have a small binary size. (Optimization takes time to complete.)")
@@ -102,6 +111,7 @@ pub fn build_app<'a>() -> Command<'a> {
         .subcommand(Command::new(CMD_BUILD)
             .about("Build a binary from the given .roc file, but don't run it")
             .arg(flag_optimize.clone())
+            .arg(flag_max_threads.clone())
             .arg(flag_opt_size.clone())
             .arg(flag_dev.clone())
             .arg(flag_debug.clone())
@@ -141,6 +151,7 @@ pub fn build_app<'a>() -> Command<'a> {
         .subcommand(Command::new(CMD_RUN)
             .about("Run a .roc file even if it has build errors")
             .arg(flag_optimize.clone())
+            .arg(flag_max_threads.clone())
             .arg(flag_opt_size.clone())
             .arg(flag_dev.clone())
             .arg(flag_debug.clone())
@@ -193,6 +204,7 @@ pub fn build_app<'a>() -> Command<'a> {
         )
         .trailing_var_arg(true)
         .arg(flag_optimize)
+            .arg(flag_max_threads.clone())
         .arg(flag_opt_size)
         .arg(flag_dev)
         .arg(flag_debug)