diff --git a/src/babashka/process.cljc b/src/babashka/process.cljc
index 20a30f4..1fffd81 100644
--- a/src/babashka/process.cljc
+++ b/src/babashka/process.cljc
@@ -237,6 +237,7 @@
                  :env
                  :extra-env
                  :escape]} opts
+         dir (str dir) ;; convert Path or File into String
          str-fn (comp escape str)
          cmd (mapv str-fn cmd)
          cmd (if-let [program-resolver (:program-resolver opts)]
diff --git a/test/babashka/process_test.cljc b/test/babashka/process_test.cljc
index 66bd644..310f4cc 100644
--- a/test/babashka/process_test.cljc
+++ b/test/babashka/process_test.cljc
@@ -162,7 +162,7 @@
   ;; It would be nice to use clojure, but on Windows the official install
   ;; is still currently a PowerShell Module, which cannot be spawned directly.
   ;; So we'll use java. This test assumes that java and javac are on the PATH."
-  (let [test-dir "target/process-dir-option-test"
+  (let [test-dir (fs/path "target/process-dir-option-test")
         java (fs/which "java")
         java-dir (-> java fs/parent fs/canonicalize str)
         java-src (-> (fs/file test-dir "UserDir.java") str)