diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index 0f27028..87a99f3 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.10", "3.11", "3.12",]
+        python-version: ["3.9", "3.10", "3.11", "3.12",]
         os: [windows-latest, macOS-latest, ubuntu-latest,]
 
     steps:
diff --git a/calcpy/transformers.py b/calcpy/transformers.py
index a4a624c..cf2426c 100644
--- a/calcpy/transformers.py
+++ b/calcpy/transformers.py
@@ -155,7 +155,7 @@ def auto_prod_replace(match):
         try:
             ip.compile.ast_parse(code)
         except Exception as e:
-            if isinstance(e, SyntaxError) and 'cannot assign to expression' in str(e):
+            if isinstance(e, SyntaxError) and 'cannot assign to ' in str(e):
                 code = re.sub(r'(.*[^=])=([^=].*)', r'solve(Eq(\1, \2))', code)
 
     if ip.calcpy._print_transformed_code: