diff --git a/src/c/assignment.d b/src/c/assignment.d
index 592816806..a3ca7866c 100644
--- a/src/c/assignment.d
+++ b/src/c/assignment.d
@@ -69,13 +69,13 @@ static void
 ecl_rem_setf_definition(cl_object sym)
 {
 	cl_env_ptr the_env = ecl_process_env();
-        ECL_WITH_GLOBAL_ENV_RDLOCK_BEGIN(the_env) {
+        ECL_WITH_GLOBAL_ENV_WRLOCK_BEGIN(the_env) {
                 cl_object pair = ecl_gethash_safe(sym, cl_core.setf_definitions, Cnil);
 		if (!Null(pair)) {
-			ECL_RPLACA(sym, Cnil);
+			ECL_RPLACA(pair, Cnil);
 			ecl_remhash(sym, cl_core.setf_definitions);
 		}
-        } ECL_WITH_GLOBAL_ENV_RDLOCK_END;
+        } ECL_WITH_GLOBAL_ENV_WRLOCK_END;
 }
 
 @(defun si::fset (fname def &optional macro pprint)
diff --git a/src/c/reference.d b/src/c/reference.d
index 5b5a62763..1a988427a 100644
--- a/src/c/reference.d
+++ b/src/c/reference.d
@@ -62,8 +62,10 @@ cl_fboundp(cl_object fname)
 			if (CONSP(sym) && CDR(sym) == Cnil) {
 				cl_object pair;
 				sym = CAR(sym);
-				pair = ecl_setf_definition(sym, Cnil);
-				@(return ecl_cdr(pair))
+				if (ECL_SYMBOLP(sym)) {
+					pair = ecl_setf_definition(sym, Cnil);
+					@(return ecl_cdr(pair));
+				}
 			}
 		}
 	}