diff --git a/src/parser.cpp b/src/parser.cpp
index e44744e24..92c33b706 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -644,22 +644,18 @@ int parser_t::eval(wcstring cmd, const io_chain_t &io, enum block_type_t block_t
         fwprintf(stderr, L"%ls\n", backtrace_and_desc.c_str());
         return 1;
     }
-    return this->eval(ps, io, block_type);
+    this->eval(ps, io, block_type);
+    return 0;
 }
 
-int parser_t::eval(parsed_source_ref_t ps, const io_chain_t &io, enum block_type_t block_type) {
+void parser_t::eval(parsed_source_ref_t ps, const io_chain_t &io, enum block_type_t block_type) {
     CHECK_BLOCK(1);
     assert(block_type == TOP || block_type == SUBST);
-
-    if (ps->tree.empty()) {
-        return 0;
+    if (!ps->tree.empty()) {
+        // Execute the first node.
+        tnode_t<grammar::job_list> start{&ps->tree, &ps->tree.front()};
+        this->eval_node(ps, start, io, block_type);
     }
-
-    // Execute the first node.
-    tnode_t<grammar::job_list> start{&ps->tree, &ps->tree.front()};
-    this->eval_node(ps, start, io, block_type);
-
-    return 0;
 }
 
 template <typename T>
diff --git a/src/parser.h b/src/parser.h
index 289f8b8ae..35ca8922f 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -238,11 +238,11 @@ class parser_t {
     /// \param io io redirections to perform on all started jobs
     /// \param block_type The type of block to push on the block stack
     ///
-    /// \return 0 on success, 1 otherwise
+    /// \return 0 on success, 1 on a parse error.
     int eval(wcstring cmd, const io_chain_t &io, enum block_type_t block_type);
 
     /// Evaluate the parsed source ps.
-    int eval(parsed_source_ref_t ps, const io_chain_t &io, enum block_type_t block_type);
+    void eval(parsed_source_ref_t ps, const io_chain_t &io, enum block_type_t block_type);
 
     /// Evaluates a node.
     /// The node type must be grammar::statement or grammar::job_list.