diff --git a/dom/canvas/test/webgl-conf/generated-mochitest.ini b/dom/canvas/test/webgl-conf/generated-mochitest.ini
index ea27cf0350fb..7961c701ad46 100644
--- a/dom/canvas/test/webgl-conf/generated-mochitest.ini
+++ b/dom/canvas/test/webgl-conf/generated-mochitest.ini
@@ -7835,7 +7835,7 @@ fail-if = (os == 'android' && android_version == '10')
 [generated/test_conformance__glsl__misc__shader-precision-format-obeyed.html]
 [generated/test_conformance__glsl__misc__shader-struct-scope.html]
 [generated/test_conformance__glsl__misc__shader-uniform-packing-restrictions.html]
-skip-if = (os == 'android') || (os == 'win' && os_version == '6.1' && debug)
+skip-if = (os == 'android') || (os == 'win' && os_version == '6.1' && debug) || (os == 'linux' && debug)
 [generated/test_conformance__glsl__misc__shader-varying-packing-restrictions.html]
 [generated/test_conformance__glsl__misc__shader-with-256-character-define.html]
 [generated/test_conformance__glsl__misc__shader-with-256-character-identifier.frag.html]
diff --git a/dom/canvas/test/webgl-conf/mochitest-errata.ini b/dom/canvas/test/webgl-conf/mochitest-errata.ini
index 063979cfd359..700055707f83 100644
--- a/dom/canvas/test/webgl-conf/mochitest-errata.ini
+++ b/dom/canvas/test/webgl-conf/mochitest-errata.ini
@@ -533,8 +533,8 @@ skip-if = (os == 'android')
 [generated/test_conformance__context__context-release-with-workers.html]
 skip-if = (os == 'android')
 [generated/test_conformance__glsl__misc__shader-uniform-packing-restrictions.html]
-# Frequent timeout on win7 debug.
-skip-if = (os == 'android') || (os == 'win' && os_version == '6.1' && debug)
+# Frequent timeout on win7 and linux debug.
+skip-if = (os == 'android') || (os == 'win' && os_version == '6.1' && debug) || (os == 'linux' && debug)
 [generated/test_conformance__glsl__bugs__complex-glsl-does-not-crash.html]
 skip-if = (os == 'android')