diff --git a/core/inference/known-words/known-words.factor b/core/inference/known-words/known-words.factor
index ff5fc478ca..2d45ce0d0c 100755
--- a/core/inference/known-words/known-words.factor
+++ b/core/inference/known-words/known-words.factor
@@ -356,7 +356,7 @@ M: object infer-call
 
 \ setenv { object fixnum } { } <effect> set-primitive-effect
 
-\ exists? { string } { object } <effect> set-primitive-effect
+\ (exists?) { string } { object } <effect> set-primitive-effect
 
 \ (directory) { string } { array } <effect> set-primitive-effect
 
diff --git a/core/io/files/files-tests.factor b/core/io/files/files-tests.factor
index 2c9d883695..20eb662fc7 100755
--- a/core/io/files/files-tests.factor
+++ b/core/io/files/files-tests.factor
@@ -3,6 +3,9 @@ USING: tools.test io.files io.files.private io threads kernel
 continuations io.encodings.ascii io.files.unique sequences
 strings accessors io.encodings.utf8 math ;
 
+\ exists? must-infer
+\ (exists?) must-infer
+
 [ ] [ "blahblah" temp-file dup exists? [ delete-directory ] [ drop ] if ] unit-test
 [ ] [ "blahblah" temp-file make-directory ] unit-test
 [ t ] [ "blahblah" temp-file directory? ] unit-test