diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 93537fe..64fabe4 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -29,7 +29,7 @@ jobs:
 
       - name: Test parsing 'go.mod'
         run: |
-          bin/parse-legacy-file test-fixtures/go.mod | grep "^1.19.3"
+          bin/parse-legacy-file test-fixtures/go.mod | grep "^1.18.6"
       - name: Test parsing '.go-version'
         run: |
           bin/parse-legacy-file test-fixtures/.go-version | grep "^1.17.13"
diff --git a/bin/parse-legacy-file b/bin/parse-legacy-file
index c6f0e13..4c1af63 100755
--- a/bin/parse-legacy-file
+++ b/bin/parse-legacy-file
@@ -34,7 +34,7 @@ get_legacy_version() {
         sed -E \
           -e 's/.*heroku goVersion //' \
           -e 's/[[:space:]]//' \
-          -e 's/go([0-9]+).*/\1/' |
+          -e 's/go([1-9][[:digit:]]*\.[[:digit:]]+(\.[[:digit:]]+)?)/\1/' |
         head -1
     )
   elif [ -e "$current_file" ]; then