diff --git a/dom/plugins/base/nsNPAPIPlugin.cpp b/dom/plugins/base/nsNPAPIPlugin.cpp
index 8882916b4f4a..7caab1bc04ed 100644
--- a/dom/plugins/base/nsNPAPIPlugin.cpp
+++ b/dom/plugins/base/nsNPAPIPlugin.cpp
@@ -693,7 +693,6 @@ AsyncCallbackAutoLock::~AsyncCallbackAutoLock()
   }
 }
 
-
 NPP NPPStack::sCurrentNPP = nullptr;
 
 const char *
@@ -744,7 +743,6 @@ _geturl(NPP npp, const char* relativeURL, const char* target)
       (strncmp(relativeURL, "ftp:", 4) != 0)) {
     nsNPAPIPluginInstance *inst = (nsNPAPIPluginInstance *) npp->ndata;
 
-
     const char *name = nullptr;
     RefPtr<nsPluginHost> host = nsPluginHost::GetInst();
     host->GetPluginName(inst, &name);
@@ -1958,9 +1956,7 @@ _getvalue(NPP npp, NPNVariable variable, void *result)
         return NPERR_NO_ERROR;
       }
     }
-    else {
-      return NPERR_GENERIC_ERROR;
-    }
+    return NPERR_GENERIC_ERROR;
   }
 
 #ifndef NP_NO_QUICKDRAW
@@ -2189,14 +2185,13 @@ _getvalue(NPP npp, NPNVariable variable, void *result)
 
   // we no longer hand out any XPCOM objects
   case NPNVDOMElement:
-    // fall through
   case NPNVDOMWindow:
-    // fall through
   case NPNVserviceManager:
     // old XPCOM objects, no longer supported, but null out the out
     // param to avoid crashing plugins that still try to use this.
     *(nsISupports**)result = nullptr;
-    // fall through
+    MOZ_FALLTHROUGH;
+
   default:
     NPN_PLUGIN_LOG(PLUGIN_LOG_NORMAL, ("NPN_getvalue unhandled get value: %d\n", variable));
     return NPERR_GENERIC_ERROR;
diff --git a/dom/plugins/ipc/PluginInstanceChild.cpp b/dom/plugins/ipc/PluginInstanceChild.cpp
index f6dee021c5af..5802dc3cd675 100644
--- a/dom/plugins/ipc/PluginInstanceChild.cpp
+++ b/dom/plugins/ipc/PluginInstanceChild.cpp
@@ -502,6 +502,7 @@ PluginInstanceChild::NPN_GetValue(NPNVariable aVar,
     case NPNVSupportsXEmbedBool:
     case NPNVSupportsWindowless:
         NS_NOTREACHED("NPNVariable should be handled in PluginModuleChild.");
+        MOZ_FALLTHROUGH;
 #endif
 
     default:
@@ -510,7 +511,6 @@ PluginInstanceChild::NPN_GetValue(NPNVariable aVar,
                 (int) aVar, NPNVariableToString(aVar)));
         return NPERR_GENERIC_ERROR;
     }
-
 }
 
 #ifdef MOZ_WIDGET_COCOA
@@ -2313,7 +2313,6 @@ PluginInstanceChild::EnumThreadWindowsCallback(HWND hWnd,
     return TRUE;
 }
 
-
 void
 PluginInstanceChild::SetupFlashMsgThrottle()
 {
@@ -2610,7 +2609,6 @@ StreamNotifyChild::ActorDestroy(ActorDestroyReason why)
     }
 }
 
-
 void
 StreamNotifyChild::SetAssociatedStream(BrowserStreamChild* bs)
 {