diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index acd376d..f2c813e 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -139,7 +139,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        package: [ calcos, hstcal ]
+        package: [ calcos, hstcal, stsynphot ]
         python: [ '3.8', '3.9', '3.10' ]
         os: [ ubuntu-latest, macos-latest ]
         include: