diff --git a/plrust-tests/src/trusted.rs b/plrust-tests/src/trusted.rs
index 33b373a6..04986420 100644
--- a/plrust-tests/src/trusted.rs
+++ b/plrust-tests/src/trusted.rs
@@ -190,31 +190,32 @@ mod tests {
 
     #[pg_test]
     #[search_path(@extschema@)]
-    #[should_panic = "error: the `env` and `option_env` macros are forbidden"]
+    #[should_panic = "environment variable `FOOBAR` not defined at compile time"]
     #[cfg(feature = "trusted")]
     fn plrust_block_env() -> spi::Result<()> {
         let definition = r#"
-            CREATE FUNCTION get_path() RETURNS text AS $$
-                let path = env!("PATH");
-                Ok(Some(path.to_string()))
+            CREATE FUNCTION get_foobar() RETURNS text AS $$
+                let foo = env!("FOOBAR");
+                Ok(Some(foo.to_string()))
             $$ LANGUAGE plrust;
         "#;
+        std::env::set_var("FOOBAR", "1");
         Spi::run(definition)
     }
 
     #[pg_test]
     #[search_path(@extschema@)]
-    #[should_panic = "error: the `env` and `option_env` macros are forbidden"]
+    #[should_panic = "the `option_env` macro always returns `None` in the PL/Rust user function"]
     #[cfg(feature = "trusted")]
     fn plrust_block_option_env() -> spi::Result<()> {
         let definition = r#"
-            CREATE FUNCTION try_get_path() RETURNS text AS $$
-                match option_env!("PATH") {
-                    None => Ok(None),
-                    Some(s) => Ok(Some(s.to_string()))
-                }
+            CREATE FUNCTION try_get_foobar2() RETURNS text AS $$
+                let v = option_env!("FOOBAR2")
+                    .expect("the `option_env` macro always returns `None` in the PL/Rust user function");
+                Ok(Some(v.to_string()))
             $$ LANGUAGE plrust;
         "#;
+        std::env::set_var("FOOBAR2", "1");
         Spi::run(definition)
     }
 
diff --git a/plrustc/plrustc/src/main.rs b/plrustc/plrustc/src/main.rs
index 2d712d6e..47ac19bb 100644
--- a/plrustc/plrustc/src/main.rs
+++ b/plrustc/plrustc/src/main.rs
@@ -50,6 +50,16 @@ impl Callbacks for PlrustcCallbacks {
     }
 }
 
+fn clear_env() {
+    for (name, _) in std::env::vars_os() {
+        // Can't remove `PATH`, need it to locate linker and such.
+        if name == "PATH" {
+            continue;
+        }
+        std::env::remove_var(name);
+    }
+}
+
 fn main() {
     rustc_driver::install_ice_hook("https://github.com/tcdi/plrust/issues/new", |_| ());
     let handler = &EarlyErrorHandler::new(ErrorOutputType::default());
@@ -58,6 +68,9 @@ fn main() {
         let args =
             rustc_driver::args::arg_expand_all(handler, &std::env::args().collect::<Vec<_>>());
         let config = PlrustcConfig::from_env_and_args(&args);
+        if config.compiling_user_crate() {
+            clear_env();
+        }
         run_compiler(
             args,
             &mut PlrustcCallbacks {