diff --git a/toolkit/components/aboutmemory/content/aboutMemory.js b/toolkit/components/aboutmemory/content/aboutMemory.js
index fe5789155ffc..809eb4ae953d 100644
--- a/toolkit/components/aboutmemory/content/aboutMemory.js
+++ b/toolkit/components/aboutmemory/content/aboutMemory.js
@@ -483,6 +483,9 @@ function updateAboutMemoryFromReporters()
 }
 
 // Increment this if the JSON format changes.
+//
+// If/when this changes to 2, the beLenient() function and its use can be
+// removed.
 var gCurrentFileFormatVersion = 1;
 
 /**
@@ -958,8 +961,29 @@ function getPCollsByProcess(aProcessReports)
                   "non-sentence explicit description");
 
     } else {
-      assertInput(gSentenceRegExp.test(aDescription),
-                  "non-sentence other description");
+      const kLenientPrefixes =
+        ['rss/', 'pss/', 'size/', 'swap/', 'compartments/', 'ghost-windows/'];
+      let beLenient = function(aUnsafePath) {
+        for (let i = 0; i < kLenientPrefixes.length; i++) {
+          if (aUnsafePath.startsWith(kLenientPrefixes[i])) {
+            return true;
+          }
+        }
+        return false;
+      }
+
+      // In general, non-explicit reports should have a description that is a
+      // complete sentence.  However, we want to be able to read old saved
+      // reports, so we are lenient in a couple of situations where we used to
+      // allow non-sentence descriptions:
+      // - smaps reports (which were removed in bug 912165);
+      // - compartment and ghost-window reports (which had empty descriptions
+      //   prior to bug 911641).
+      if (!beLenient(aUnsafePath)) {
+        assertInput(gSentenceRegExp.test(aDescription),
+                    "non-sentence other description: " + aUnsafePath + ", " +
+                    aDescription);
+      }
     }
 
     assert(aPresence === undefined ||
diff --git a/toolkit/components/aboutmemory/tests/memory-reports-good.json b/toolkit/components/aboutmemory/tests/memory-reports-good.json
index 8c5c2412a54f..f3ec6ff4b003 100644
--- a/toolkit/components/aboutmemory/tests/memory-reports-good.json
+++ b/toolkit/components/aboutmemory/tests/memory-reports-good.json
@@ -7,6 +7,13 @@
     {"process": "Main Process (pid NNN)", "path": "other/a", "kind": 2, "units": 0, "amount": 209715, "description": "Other a."},
     {"process": "Main Process (pid NNN)", "path": "explicit/a/b", "kind": 1, "units": 0, "amount": 52428800, "description": "A b."},
 
+    {"process": "Main Process (pid NNN)", "path": "size/a", "kind": 1, "units": 0, "amount": 1024, "description": "non-sentence"},
+    {"process": "Main Process (pid NNN)", "path": "rss/a", "kind": 1, "units": 0, "amount": 1024, "description": "non-sentence"},
+    {"process": "Main Process (pid NNN)", "path": "pss/a", "kind": 1, "units": 0, "amount": 1024, "description": "non-sentence"},
+    {"process": "Main Process (pid NNN)", "path": "swap/a", "kind": 1, "units": 0, "amount": 1024, "description": "non-sentence"},
+    {"process": "Main Process (pid NNN)", "path": "compartments/system/a", "kind": 1, "units": 0, "amount": 1024, "description": ""},
+    {"process": "Main Process (pid NNN)", "path": "ghost-windows/a", "kind": 1, "units": 0, "amount": 1024, "description": ""},
+
     {"process": "Explicit-only process", "path": "explicit/a/b", "kind": 1, "units": 0, "amount": 100000, "description": "A b."},
 
     {"process": "Other-only process", "path": "a/b", "kind": 1, "units": 0, "amount": 100000, "description": "A b."},
diff --git a/toolkit/components/aboutmemory/tests/test_aboutmemory3.xul b/toolkit/components/aboutmemory/tests/test_aboutmemory3.xul
index 38c55f7d858b..a99a1c175e89 100644
--- a/toolkit/components/aboutmemory/tests/test_aboutmemory3.xul
+++ b/toolkit/components/aboutmemory/tests/test_aboutmemory3.xul
@@ -213,10 +213,28 @@ Explicit Allocations\n\
 \n\
 Other Measurements\n\
 \n\
+1,024 B (100.0%) -- compartments\n\
+└──1,024 B (100.0%) ── system/a\n\
+\n\
+1,024 B (100.0%) -- ghost-windows\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
 314,572 B (100.0%) -- other\n\
 ├──209,715 B (66.67%) ── a\n\
 └──104,857 B (33.33%) ── b\n\
 \n\
+1,024 B (100.0%) -- pss\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
+1,024 B (100.0%) -- rss\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
+1,024 B (100.0%) -- size\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
+1,024 B (100.0%) -- swap\n\
+└──1,024 B (100.0%) ── a\n\
+\n\
 262,144,000 B ── heap-allocated\n\
 \n\
 Other-only process\n\
@@ -309,12 +327,13 @@ Other Measurements\n\
     // This loads a pre-existing file that is valid.
     { filename: "memory-reports-good.json", expected: expectedGood, dumpFirst: false },
 
-    // This dumps to a file and then reads it back in.  The output is the same as the first test.
+    // This dumps to a file and then reads it back in.
     { filename: "memory-reports-dumped.json.gz", expected: expectedGood2, dumpFirst: true },
 
     // This loads a pre-existing file that is invalid.
     { filename: "memory-reports-bad.json",  expected: expectedBad, dumpFirst: false },
 
+    // This loads a pre-existing diff file.
     { filename: "memory-reports-diff1.json", filename2: "memory-reports-diff2.json",  expected: expectedDiff, dumpFirst: false }
   ];
 
diff --git a/toolkit/components/aboutmemory/tests/test_aboutmemory4.xul b/toolkit/components/aboutmemory/tests/test_aboutmemory4.xul
index 22ce18777e4d..000711a36ae4 100644
--- a/toolkit/components/aboutmemory/tests/test_aboutmemory4.xul
+++ b/toolkit/components/aboutmemory/tests/test_aboutmemory4.xul
@@ -108,10 +108,28 @@ Explicit Allocations\n\
 \n\
 Other Measurements\n\
 \n\
+0.00 MB (100.0%) -- compartments\n\
+└──0.00 MB (100.0%) ── system/a\n\
+\n\
+0.00 MB (100.0%) -- ghost-windows\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
 0.30 MB (100.0%) -- other\n\
 ├──0.20 MB (66.67%) ── a\n\
 └──0.10 MB (33.33%) ── b\n\
 \n\
+0.00 MB (100.0%) -- pss\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
+0.00 MB (100.0%) -- rss\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
+0.00 MB (100.0%) -- size\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
+0.00 MB (100.0%) -- swap\n\
+└──0.00 MB (100.0%) ── a\n\
+\n\
 250.00 MB ── heap-allocated\n\
 \n\
 Other-only process\n\