diff --git a/tsconfig/all/tsconfig.json b/tsconfig/all/tsconfig.json
index 4b52ab27..90b27196 100644
--- a/tsconfig/all/tsconfig.json
+++ b/tsconfig/all/tsconfig.json
@@ -319,6 +319,9 @@
     {
       "path": "../../../ph-scale-basics"
     },
+    {
+      "path": "../../../phet-io/tsconfig.json"
+    },
     {
       "path": "../../../phet-io-test-sim"
     },