diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index c82b9a7d7b9..876c3800781 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2921,7 +2921,7 @@ typedef struct nir_block {
 
    /*
     * this node's immediate dominator in the dominance tree - set to NULL for
-    * the start block.
+    * the start block and any unreachable blocks.
     */
    struct nir_block *imm_dom;