diff --git a/documentation/technical.md b/documentation/technical.md
index 89bfa5a8..47554c18 100644
--- a/documentation/technical.md
+++ b/documentation/technical.md
@@ -349,6 +349,8 @@ The Basic Latin block is listed in full. Other blocks only where used.
 | U+2297         | ⊗     | Tensor product |
 | U+266E         | ♮     | Natural accidental |
 | U+266D         | ♭     | Flat accidental |
+| U+27E8         | ⟨     | Val angle bracket |
+| U+27E9         | ⟩     | Monzo angle bracket |
 | U+1D12A        | 𝄪     | Double-sharp accidental |
 | U+1D12B        | 𝄫     | Double-flat accidental |
 | U+1D133        | 𝄳     | Semiflat accidental |
diff --git a/src/grammars/sonic-weave.pegjs b/src/grammars/sonic-weave.pegjs
index 23367bca..df997676 100644
--- a/src/grammars/sonic-weave.pegjs
+++ b/src/grammars/sonic-weave.pegjs
@@ -72,6 +72,7 @@
     'debugger',
     'default',
     'delete',
+    'immutable',
     'match',
     'yield',
   ]);