diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index efd2392e453ed..6d09b8b09e706 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -1061,7 +1061,9 @@ pub fn parse_crate_types_from_list(list_list: Vec<String>) -> Result<Vec<CrateTy
                                        part));
                 }
             };
-            crate_types.push(new_part)
+            if !crate_types.contains(&new_part) {
+                crate_types.push(new_part)
+            }
         }
     }
 
diff --git a/src/test/run-make/duplicate-output-flavors/Makefile b/src/test/run-make/duplicate-output-flavors/Makefile
index d40b6862a0143..e33279966c971 100644
--- a/src/test/run-make/duplicate-output-flavors/Makefile
+++ b/src/test/run-make/duplicate-output-flavors/Makefile
@@ -2,3 +2,4 @@ include ../tools.mk
 
 all:
 	$(RUSTC) --crate-type=rlib foo.rs
+	$(RUSTC) --crate-type=rlib,rlib foo.rs