diff --git a/xpcom/base/MemoryPressureLevelMac.h b/xpcom/base/MemoryPressureLevelMac.h
index ec5c11ee2747..38cb49a4fd91 100644
--- a/xpcom/base/MemoryPressureLevelMac.h
+++ b/xpcom/base/MemoryPressureLevelMac.h
@@ -26,8 +26,8 @@ class MacMemoryPressureLevel {
   MacMemoryPressureLevel() : mValue(Value::eUnset) {}
   MOZ_IMPLICIT MacMemoryPressureLevel(Value aValue) : mValue(aValue) {}
 
-  bool operator==(const Value& aRhsValue) { return mValue == aRhsValue; }
-  bool operator==(const MacMemoryPressureLevel& aRhs) {
+  bool operator==(const Value& aRhsValue) const { return mValue == aRhsValue; }
+  bool operator==(const MacMemoryPressureLevel& aRhs) const {
     return mValue == aRhs.mValue;
   }
 
diff --git a/xpcom/ds/PLDHashTable.h b/xpcom/ds/PLDHashTable.h
index af17ee6fd616..67e4d7fdcf7b 100644
--- a/xpcom/ds/PLDHashTable.h
+++ b/xpcom/ds/PLDHashTable.h
@@ -222,7 +222,9 @@ class PLDHashTable {
 
     Slot& operator=(Slot&& aOther) = default;
 
-    bool operator==(const Slot& aOther) { return mEntry == aOther.mEntry; }
+    bool operator==(const Slot& aOther) const {
+      return mEntry == aOther.mEntry;
+    }
 
     PLDHashNumber KeyHash() const { return *HashPtr(); }
     void SetKeyHash(PLDHashNumber aHash) { *HashPtr() = aHash; }