diff --git a/libexec/pyenv-prefix b/libexec/pyenv-prefix
index 9b73795e..ac04f6bc 100755
--- a/libexec/pyenv-prefix
+++ b/libexec/pyenv-prefix
@@ -32,6 +32,7 @@ OLDIFS="$IFS"
     if [ "$version" = "system" ]; then
       if PYTHON_PATH="$(PYENV_VERSION="${version}" pyenv-which python 2>/dev/null)"; then
         PYENV_PREFIX_PATH="${PYTHON_PATH%/bin/*}"
+        PYENV_PREFIX_PATH="${PYENV_PREFIX_PATH:-/}"
       else
         echo "pyenv: system version not found in PATH" >&2
         exit 1
diff --git a/test/prefix.bats b/test/prefix.bats
index be9dbaed..6f63d1f7 100644
--- a/test/prefix.bats
+++ b/test/prefix.bats
@@ -24,6 +24,18 @@ load test_helper
   assert_success "$PYENV_TEST_DIR"
 }
 
+@test "prefix for system in /" {
+  mkdir -p "${BATS_TEST_DIRNAME}/libexec"
+  cat >"${BATS_TEST_DIRNAME}/libexec/pyenv-which" <<OUT
+#!/bin/sh
+echo /bin/python
+OUT
+  chmod +x "${BATS_TEST_DIRNAME}/libexec/pyenv-which"
+  PYENV_VERSION="system" run pyenv-prefix
+  assert_success "/"
+  rm -f "${BATS_TEST_DIRNAME}/libexec/pyenv-which"
+}
+
 @test "prefix for invalid system" {
   PATH="$(path_without python)" run pyenv-prefix system
   assert_failure "pyenv: system version not found in PATH"