diff --git a/act/runner/run_context.go b/act/runner/run_context.go
index f8e8782f..2f0cce32 100644
--- a/act/runner/run_context.go
+++ b/act/runner/run_context.go
@@ -402,13 +402,13 @@ func (rc *RunContext) getNetworkName(_ context.Context) (networkName string, cre
 	return networkName, createAndDeleteNetwork
 }
 
-var sanitizeNetworkAliasRegex = regexp.MustCompile("[^A-Z0-9-]")
+var sanitizeNetworkAliasRegex = regexp.MustCompile("[^a-z0-9-]")
 
 func sanitizeNetworkAlias(ctx context.Context, original string) string {
-	sanitized := sanitizeNetworkAliasRegex.ReplaceAllString(strings.ToUpper(original), "_")
+	sanitized := sanitizeNetworkAliasRegex.ReplaceAllString(strings.ToLower(original), "_")
 	if sanitized != original {
 		logger := common.Logger(ctx)
-		logger.Infof("The network alias is %s (sanitized version of %s)", original, sanitized)
+		logger.Infof("The network alias is %s (sanitized version of %s)", sanitized, original)
 	}
 	return sanitized
 }
diff --git a/act/runner/run_context_test.go b/act/runner/run_context_test.go
index 0c2a3c86..8c362b3a 100644
--- a/act/runner/run_context_test.go
+++ b/act/runner/run_context_test.go
@@ -712,10 +712,10 @@ func Test_createSimpleContainerName(t *testing.T) {
 }
 
 func TestSanitizeNetworkAlias(t *testing.T) {
-	same := "SAME"
+	same := "same"
 	assert.Equal(t, same, sanitizeNetworkAlias(context.Background(), same))
-	original := "OR.IGIN'A-L"
-	sanitized := "OR_IGIN_A-L"
+	original := "or.igin'A-L"
+	sanitized := "or_igin_a-l"
 	assert.Equal(t, sanitized, sanitizeNetworkAlias(context.Background(), original))
 }