diff --git a/cc/bp2build.go b/cc/bp2build.go
index d891007..fa30d09 100644
--- a/cc/bp2build.go
+++ b/cc/bp2build.go
@@ -376,7 +376,8 @@
 				return
 			}
 			if ca.stl == nil {
-				ca.stl = stlProps.Stl
+				stl := deduplicateStlInput(*stlProps.Stl)
+				ca.stl = &stl
 			} else if ca.stl != stlProps.Stl {
 				ctx.ModuleErrorf("Unsupported conversion: module with different stl for different variants: %s and %s", *ca.stl, stlProps.Stl)
 			}