diff --git a/compiler/internal/env/env.go b/compiler/internal/env/env.go
index 1088de59..09246f60 100644
--- a/compiler/internal/env/env.go
+++ b/compiler/internal/env/env.go
@@ -41,8 +41,12 @@ func LLGoRuntimeDir() string {
 }
 
 func LLGoROOT() string {
-	if root, ok := isLLGoRoot(os.Getenv("LLGO_ROOT")); ok {
-		return root
+	llgoRootEnv := os.Getenv("LLGO_ROOT")
+	if llgoRootEnv != "" {
+		if root, ok := isLLGoRoot(llgoRootEnv); ok {
+			return root
+		}
+		fmt.Fprintf(os.Stderr, "WARNING: LLGO_ROOT is not a valid LLGO root: %s\n", llgoRootEnv)
 	}
 	// Get executable path
 	exe, err := os.Executable()
diff --git a/compiler/internal/env/env_test.go b/compiler/internal/env/env_test.go
index 0bb19cdb..823edeeb 100644
--- a/compiler/internal/env/env_test.go
+++ b/compiler/internal/env/env_test.go
@@ -58,10 +58,28 @@ func TestLLGoRuntimeDir(t *testing.T) {
 		defer os.Setenv("LLGO_ROOT", origLLGoRoot)
 
 		os.Setenv("LLGO_ROOT", "/nonexistent/path")
-		wd, _ := os.Getwd()
-		expected, _ := filepath.Abs(filepath.Join(wd, "../../../runtime"))
-		if got := LLGoRuntimeDir(); got != expected {
-			t.Errorf("LLGoRuntimeDir() = %v, want %v", got, expected)
+		wd, err := os.Getwd()
+		if err != nil {
+			t.Fatal(err)
+		}
+		runtimeDir := filepath.Join(wd, "../../../runtime")
+		if got := LLGoRuntimeDir(); got != runtimeDir {
+			t.Errorf("LLGoRuntimeDir() = %v, want %v", got, runtimeDir)
+		}
+	})
+
+	t.Run("devel runtime dir", func(t *testing.T) {
+		origLLGoRoot := os.Getenv("LLGO_ROOT")
+		defer os.Setenv("LLGO_ROOT", origLLGoRoot)
+
+		os.Setenv("LLGO_ROOT", "")
+		wd, err := os.Getwd()
+		if err != nil {
+			t.Fatal(err)
+		}
+		runtimeDir := filepath.Join(wd, "../../../runtime")
+		if got := LLGoRuntimeDir(); got != runtimeDir {
+			t.Errorf("LLGoRuntimeDir() = %v, want %v", got, runtimeDir)
 		}
 	})
 }
@@ -92,8 +110,13 @@ func TestLLGoROOT(t *testing.T) {
 		defer os.Setenv("LLGO_ROOT", origLLGoRoot)
 
 		os.Setenv("LLGO_ROOT", "/nonexistent/path")
-		if got := LLGoROOT(); got != "" {
-			t.Errorf("LLGoROOT() = %v, want empty string", got)
+		wd, err := os.Getwd()
+		if err != nil {
+			t.Fatal(err)
+		}
+		rootDir := filepath.Join(wd, "../../..")
+		if got := LLGoROOT(); got != rootDir {
+			t.Errorf("LLGoROOT() = %v, want %v", got, rootDir)
 		}
 	})