diff --git a/dom/security/nsCSPContext.cpp b/dom/security/nsCSPContext.cpp
index 5e435d4ca8..a7517f65e8 100644
--- a/dom/security/nsCSPContext.cpp
+++ b/dom/security/nsCSPContext.cpp
@@ -219,14 +219,6 @@ nsCSPContext::permitsInternal(CSPDirective aDir,
nsAutoString violatedDirective;
for (uint32_t p = 0; p < mPolicies.Length(); p++) {
-
- // According to the W3C CSP spec, frame-ancestors checks are ignored for
- // report-only policies (when "monitoring").
- if (aDir == nsIContentSecurityPolicy::FRAME_ANCESTORS_DIRECTIVE &&
- mPolicies[p]->getReportOnlyFlag()) {
- continue;
- }
-
if (!mPolicies[p]->permits(aDir,
aContentLocation,
aNonce,
diff --git a/dom/security/test/csp/file_frame_ancestors_ro.html b/dom/security/test/csp/file_frame_ancestors_ro.html
new file mode 100644
index 0000000000..ff5ae9cf9f
--- /dev/null
+++ b/dom/security/test/csp/file_frame_ancestors_ro.html
@@ -0,0 +1 @@
+Child Document
diff --git a/dom/security/test/csp/file_frame_ancestors_ro.html^headers^ b/dom/security/test/csp/file_frame_ancestors_ro.html^headers^
new file mode 100644
index 0000000000..d018af3a96
--- /dev/null
+++ b/dom/security/test/csp/file_frame_ancestors_ro.html^headers^
@@ -0,0 +1 @@
+Content-Security-Policy-Report-Only: frame-ancestors 'none'; report-uri http://mochi.test:8888/foo.sjs
diff --git a/dom/security/test/csp/mochitest.ini b/dom/security/test/csp/mochitest.ini
index ca5c2c6eab..33b1120202 100644
--- a/dom/security/test/csp/mochitest.ini
+++ b/dom/security/test/csp/mochitest.ini
@@ -91,6 +91,8 @@ support-files =
file_bug941404.html
file_bug941404_xhr.html
file_bug941404_xhr.html^headers^
+ file_frame_ancestors_ro.html
+ file_frame_ancestors_ro.html^headers^
file_hash_source.html
file_dual_header_testserver.sjs
file_hash_source.html^headers^
@@ -240,6 +242,7 @@ skip-if = toolkit == 'android' # Times out, not sure why (bug 1008445)
[test_bug910139.html]
[test_bug909029.html]
[test_bug1229639.html]
+[test_frame_ancestors_ro.html]
[test_policyuri_regression_from_multipolicy.html]
[test_nonce_source.html]
[test_bug941404.html]
diff --git a/dom/security/test/csp/test_frame_ancestors_ro.html b/dom/security/test/csp/test_frame_ancestors_ro.html
new file mode 100644
index 0000000000..90f68e25eb
--- /dev/null
+++ b/dom/security/test/csp/test_frame_ancestors_ro.html
@@ -0,0 +1,69 @@
+
+
+
+ Test for frame-ancestors support in Content-Security-Policy-Report-Only
+
+
+
+
+
+
+
+