diff --git a/CMakeLists.txt b/CMakeLists.txt
index d8f241bed..e42ec45a7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,4 @@
-# CMake 3.19 is needed for file(REAL_PATH)
-cmake_minimum_required(VERSION 3.19)
+cmake_minimum_required(VERSION 3.5)
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/cmake")
 
diff --git a/build.rs b/build.rs
index 6284b7e3e..59fb29179 100644
--- a/build.rs
+++ b/build.rs
@@ -15,6 +15,8 @@ fn main() {
     // OUT_DIR is set by Cargo when the build script is running (not compiling)
     let default_build_dir = env::var("OUT_DIR").unwrap();
     let build_dir = option_env!("FISH_BUILD_DIR").unwrap_or(&default_build_dir);
+    let build_dir = std::fs::canonicalize(build_dir).unwrap();
+    let build_dir = build_dir.to_str().unwrap();
     rsconf::set_env_value("FISH_BUILD_DIR", build_dir);
     // We need to canonicalize (i.e. realpath) the manifest dir because we want to be able to
     // compare it directly as a string at runtime.
diff --git a/cmake/Rust.cmake b/cmake/Rust.cmake
index 36bc34ea3..057262a41 100644
--- a/cmake/Rust.cmake
+++ b/cmake/Rust.cmake
@@ -29,9 +29,6 @@ if(DEFINED WITH_GETTEXT AND NOT "${WITH_GETTEXT}")
     set(CMAKE_WITH_GETTEXT "0")
 endif()
 
-# CMAKE_BINARY_DIR can include symlinks, since we want to compare this to the dir fish is executed in we need to canonicalize it.
-file(REAL_PATH "${CMAKE_BINARY_DIR}" fish_binary_dir)
-
 if(FISH_CRATE_FEATURES)
     set(FEATURES_ARG ${FISH_CRATE_FEATURES})
     list(PREPEND FEATURES_ARG "--features")
@@ -44,7 +41,7 @@ get_property(
 
 # Tell Cargo where our build directory is so it can find Cargo.toml.
 set(VARS_FOR_CARGO
-    "FISH_BUILD_DIR=${fish_binary_dir}"
+    "FISH_BUILD_DIR=${CMAKE_BINARY_DIR}"
     "PREFIX=${CMAKE_INSTALL_PREFIX}"
     # Temporary hack to propogate CMake flags/options to build.rs.
     "CMAKE_WITH_GETTEXT=${CMAKE_WITH_GETTEXT}"