diff --git a/src/protocol/eval/executor.rs b/src/protocol/eval/executor.rs
index 68dc3eec80a2ebb90159a4d62401f7eb6c5a727d..aded401d18af5b9c3253fe43f2183f73167db1b4 100644
--- a/src/protocol/eval/executor.rs
+++ b/src/protocol/eval/executor.rs
@@ -200,6 +200,7 @@ pub enum EvalContinuation {
     SyncBlockEnd,
     NewComponent(DefinitionId, i32, ValueGroup),
     NewChannel,
+    NewFork,
     BlockFires(PortId),
     BlockGet(PortId),
     Put(PortId, Value),
@@ -886,6 +887,33 @@ impl Prompt {
 
                 Ok(EvalContinuation::SyncBlockEnd)
             },
+            Statement::Fork(stmt) => {
+                if stmt.right_body.is_none() {
+                    // No reason to fork
+                    cur_frame.position = stmt.left_body.upcast();
+                } else {
+                    // Need to fork
+                    if let Some(go_left) = ctx.get_fork() {
+                        // Runtime has created a fork
+                        if go_left {
+                            cur_frame.position = stmt.left_body.upcast();
+                        } else {
+                            cur_frame.position = stmt.right_body.unwrap().upcast();
+                        }
+                    } else {
+                        // Request the runtime to create a fork of the current
+                        // branch
+                        return Ok(EvalContinuation::NewFork);
+                    }
+                }
+
+                Ok(EvalContinuation::Stepping)
+            },
+            Statement::EndFork(stmt) => {
+                cur_frame.position = stmt.next;
+
+                Ok(EvalContinuation::Stepping)
+            }
             Statement::Return(_stmt) => {
                 debug_assert!(heap[cur_frame.definition].is_function());
                 debug_assert_eq!(cur_frame.expr_values.len(), 1, "expected one expr value for return statement");