diff --git a/test/node-tests/doc.test.js b/test/node-tests/doc.test.js
index b958160ad..bde7d3a52 100644
--- a/test/node-tests/doc.test.js
+++ b/test/node-tests/doc.test.js
@@ -99,7 +99,7 @@ const knownProblems = new Set([
   'mod', 'invmod', 'floor', 'fix', 'expm1', 'exp', 'dotPow', 'dotMultiply',
   'dotDivide', 'divide', 'ceil', 'cbrt', 'add', 'usolveAll', 'usolve', 'slu',
   'rationalize', 'qr', 'lusolve', 'lup', 'lsolveAll', 'lsolve', 'derivative',
-  'symbolicEqual', 'map', 'schur', 'sylvester'
+  'symbolicEqual', 'map', 'schur', 'sylvester', 'freqz'
 ])
 
 function maybeCheckExpectation (name, expected, expectedFrom, got, gotFrom) {
@@ -132,8 +132,9 @@ function checkExpectation (want, got) {
   if (typeof want === 'number' && typeof got === 'number' && want !== got) {
     console.log(`  Note: return value ${got} not exactly as expected: ${want}`)
     return approx.equal(got, want, 1e-9)
-  } if (typeof want !== 'undefined') {
-    approx.deepEqual(got, want)
+  }
+  if (typeof want !== 'undefined') {
+    return approx.deepEqual(got, want)
   } else {
     // don't check if we don't know what the result is supposed to be
   }