diff --git a/src/core/compile.c b/src/core/compile.c
index a4820c74..a7020993 100644
--- a/src/core/compile.c
+++ b/src/core/compile.c
@@ -958,9 +958,14 @@ JANET_CORE_FN(cfun,
     }
     const uint8_t *source = NULL;
     if (argc >= 3) {
-        source = janet_checktype(argv[2], JANET_STRING) ?
-            janet_unwrap_string(argv[2]) :
-            janet_unwrap_keyword(argv[2]);
+        Janet x = argv[2];
+        if (janet_checktype(x, JANET_STRING)) {
+            source = janet_unwrap_string(x);
+        } else if (janet_checktype(x, JANET_KEYWORD)) {
+            source = janet_unwrap_keyword(x);
+        } else {
+            janet_panic_type(x, 2, JANET_TFLAG_STRING | JANET_TFLAG_KEYWORD);
+        }
     }
     JanetArray *lints = (argc >= 4) ? janet_getarray(argv, 3) : NULL;
     JanetCompileResult res = janet_compile_lint(argv[0], env, source, lints);