diff --git a/docs/source/changelog.md b/docs/source/changelog.md
index f54478c..6511b62 100644
--- a/docs/source/changelog.md
+++ b/docs/source/changelog.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.6.1
+
+- Added support for WASM.
+
 ## 0.6.0
 
 ### Major
diff --git a/refactor/actions.py b/refactor/actions.py
index c0a12e7..30c25fa 100644
--- a/refactor/actions.py
+++ b/refactor/actions.py
@@ -96,9 +96,8 @@ def apply(self, context: Context, source: str) -> str:
         view = slice(lineno - 1, end_lineno)
         source_lines = lines[view]
 
-        indentation, start_prefix = find_indent(source_lines[-1][:col_offset])
+        indentation, start_prefix = find_indent(source_lines[0][:col_offset])
         end_suffix = source_lines[-1][end_col_offset:]
-
         replacement = split_lines(self._resynthesize(context))
         replacement.apply_indentation(
             indentation, start_prefix=start_prefix, end_suffix=end_suffix
diff --git a/refactor/runner.py b/refactor/runner.py
index 48cbd8f..53c4b7b 100644
--- a/refactor/runner.py
+++ b/refactor/runner.py
@@ -1,7 +1,6 @@
 import os
 from argparse import ArgumentParser
 from collections import defaultdict
-from concurrent.futures import ProcessPoolExecutor, as_completed
 from contextlib import nullcontext
 from functools import partial
 from itertools import chain
@@ -20,6 +19,13 @@
 
 _DEFAULT_WORKERS = object()
 
+try:
+    from concurrent.futures import ProcessPoolExecutor, as_completed
+except ImportError:
+    NO_PROCESSING = True
+else:
+    NO_PROCESSING = False
+
 
 def expand_paths(path: Path) -> Iterable[Path]:
     if path.is_file():
@@ -68,7 +74,12 @@ def run_files(
     workers = _determine_workers(workers, session.config.debug_mode)
 
     executor: ContextManager[Any]
-    if workers == 1:
+    if workers == 1 or NO_PROCESSING:
+        if workers > 1:
+            print(
+                "WARNING: multiprocessing is not available, so using the"
+                " sequential execution"
+            )
         executor = nullcontext()
         changes = (session.run_file(file) for file in files)
     else:
diff --git a/setup.cfg b/setup.cfg
index ab22a59..0ca1d52 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,6 @@
 [metadata]
 name = refactor
-version = 0.6.0
+version = 0.6.1
 description = AST-based fragmental source code refactoring toolkit
 long_description = file: README.md
 long_description_content_type = text/markdown
diff --git a/tests/test_complete_rules.py b/tests/test_complete_rules.py
index c4c9a8d..36ff38a 100644
--- a/tests/test_complete_rules.py
+++ b/tests/test_complete_rules.py
@@ -830,6 +830,36 @@ def match(self, node: ast.AST) -> Iterator[BaseAction]:
         yield Erase(node)
 
 
+class FoldMyConstants(Rule):
+    INPUT_SOURCE = """
+    result = (
+        1 * 2 + (5 + 3) # A very complex math equation
+    ) + 8 # Don't forget the 8 here
+    """
+
+    EXPECTED_SOURCE = """
+    result = 18 # Don't forget the 8 here
+    """
+
+    def match(self, node: ast.AST) -> Replace:
+        # Look for an arithmetic addition or subtraction
+        assert isinstance(node, ast.BinOp)
+        assert isinstance(op := node.op, (ast.Add, ast.Sub, ast.Mult))
+
+        # Where both left and right are constants
+        assert isinstance(left := node.left, ast.Constant)
+        assert isinstance(right := node.right, ast.Constant)
+
+        # And then replace it with the result of the computation
+        if isinstance(op, ast.Add):
+            result = ast.Constant(left.value + right.value)
+        elif isinstance(op, ast.Mult):
+            result = ast.Constant(left.value * right.value)
+        else:
+            result = ast.Constant(left.value - right.value)
+        return Replace(node, result)
+
+
 @pytest.mark.parametrize(
     "rule",
     [
@@ -844,6 +874,7 @@ def match(self, node: ast.AST) -> Iterator[BaseAction]:
         RenameImportAndDownstream,
         AssertEncoder,
         PropagateAndDelete,
+        FoldMyConstants,
     ],
 )
 def test_complete_rules(rule, tmp_path):