diff --git a/dom/bindings/ErrorResult.h b/dom/bindings/ErrorResult.h
index 7c3fc9e2f9..da7ec30e71 100644
--- a/dom/bindings/ErrorResult.h
+++ b/dom/bindings/ErrorResult.h
@@ -75,7 +75,7 @@ template<typename... Ts>
 inline bool
 ThrowErrorMessage(JSContext* aCx, const ErrNum aErrorNumber, Ts&&... aArgs)
 {
-  binding_detail::ThrowErrorMessage(aCx, static_cast<const unsigned>(aErrorNumber),
+  binding_detail::ThrowErrorMessage(aCx, static_cast<unsigned>(aErrorNumber),
                                     mozilla::Forward<Ts>(aArgs)...);
   return false;
 }
diff --git a/netwerk/cache/nsDiskCacheEntry.h b/netwerk/cache/nsDiskCacheEntry.h
index 3bec330536..506886cb7c 100644
--- a/netwerk/cache/nsDiskCacheEntry.h
+++ b/netwerk/cache/nsDiskCacheEntry.h
@@ -32,7 +32,7 @@ struct nsDiskCacheEntry {
                                     mKeySize + mMetaDataSize;
                               }
 
-    char*           Key()     { return reinterpret_cast<char*const>(this) + 
+    char*           Key()     { return reinterpret_cast<char*>(this) +
                                     sizeof(nsDiskCacheEntry);
                               }
 
diff --git a/xpcom/glue/nsTHashtable.h b/xpcom/glue/nsTHashtable.h
index 705b0294e2..830f52e881 100644
--- a/xpcom/glue/nsTHashtable.h
+++ b/xpcom/glue/nsTHashtable.h
@@ -372,7 +372,7 @@ template<class EntryType>
 PLDHashNumber
 nsTHashtable<EntryType>::s_HashKey(const void* aKey)
 {
-  return EntryType::HashKey(static_cast<const KeyTypePointer>(aKey));
+  return EntryType::HashKey(static_cast<KeyTypePointer>(aKey));
 }
 
 template<class EntryType>
@@ -381,7 +381,7 @@ nsTHashtable<EntryType>::s_MatchEntry(const PLDHashEntryHdr* aEntry,
                                       const void* aKey)
 {
   return ((const EntryType*)aEntry)->KeyEquals(
-    static_cast<const KeyTypePointer>(aKey));
+    static_cast<KeyTypePointer>(aKey));
 }
 
 template<class EntryType>
diff --git a/xpcom/string/nsReadableUtilsImpl.h b/xpcom/string/nsReadableUtilsImpl.h
index ff1497b514..94f18dffc6 100644
--- a/xpcom/string/nsReadableUtilsImpl.h
+++ b/xpcom/string/nsReadableUtilsImpl.h
@@ -18,7 +18,7 @@ inline bool IsASCII(char16_t aChar) {
 inline const char16_t* aligned(const char16_t* aPtr, const uintptr_t aMask)
 {
   return reinterpret_cast<const char16_t*>(
-      reinterpret_cast<const uintptr_t>(aPtr) & ~aMask);
+      reinterpret_cast<uintptr_t>(aPtr) & ~aMask);
 }
 
 /**