diff --git a/libraries/hfm/src/hfm/HFMFormatRegistry.cpp b/libraries/hfm/src/hfm/HFMFormatRegistry.cpp
index 1be05e99d9..2a537af151 100644
--- a/libraries/hfm/src/hfm/HFMFormatRegistry.cpp
+++ b/libraries/hfm/src/hfm/HFMFormatRegistry.cpp
@@ -14,38 +14,44 @@
 namespace hfm {
 
 FormatRegistry::MIMETypeID FormatRegistry::registerMIMEType(const MIMEType& mimeType, std::unique_ptr<Serializer::Factory>& supportedFactory) {
+    std::lock_guard<std::mutex> lock(_libraryLock);
+
     MIMETypeID id = _mimeTypeLibrary.registerMIMEType(mimeType);
-    withWriteLock([&](){
-        _supportedFormats.emplace_back(id, supportedFactory);
-    });
+    _supportedFormats.emplace_back(id, supportedFactory);
     return id;
 }
 
 void FormatRegistry::unregisterMIMEType(const MIMETypeID& mimeTypeID) {
-    withWriteLock([&](){
-        for (auto it = _supportedFormats.begin(); it != _supportedFormats.end(); it++) {
-            if ((*it).mimeTypeID == mimeTypeID) {
-                _supportedFormats.erase(it);
-                break;
-            }
+    std::lock_guard<std::mutex> lock(_libraryLock);
+
+    for (auto it = _supportedFormats.begin(); it != _supportedFormats.end(); it++) {
+        if ((*it).mimeTypeID == mimeTypeID) {
+            _supportedFormats.erase(it);
+            break;
         }
-    });
+    }
     _mimeTypeLibrary.unregisterMIMEType(mimeTypeID);
 }
 
 std::shared_ptr<Serializer> FormatRegistry::getSerializerForMIMETypeID(FormatRegistry::MIMETypeID mimeTypeID) const {
-    return resultWithReadLock<std::shared_ptr<Serializer>>([&](){
-        for (auto it = _supportedFormats.begin(); it != _supportedFormats.end(); it++) {
-            if ((*it).mimeTypeID == mimeTypeID) {
-                return (*it).factory->get();
-            }
+    // TODO: shared_lock in C++14
+    std::lock_guard<std::mutex> lock(*const_cast<std::mutex*>(&_libraryLock));
+
+    for (auto it = _supportedFormats.begin(); it != _supportedFormats.end(); it++) {
+        if ((*it).mimeTypeID == mimeTypeID) {
+            return (*it).factory->get();
         }
-        return std::shared_ptr<Serializer>();
-    });
+    }
+    return std::shared_ptr<Serializer>();
 }
 
 std::shared_ptr<Serializer> FormatRegistry::getSerializerForMIMEType(const hifi::ByteArray& data, const hifi::VariantHash& mapping, const hifi::URL& url, const std::string& webMediaType) const {
-    MIMETypeID id = _mimeTypeLibrary.findMatchingMIMEType(data, mapping, url, webMediaType);
+    MIMETypeID id;
+    {
+        // TODO: shared_lock in C++14
+        std::lock_guard<std::mutex> lock(*const_cast<std::mutex*>(&_libraryLock));
+        id = _mimeTypeLibrary.findMatchingMIMEType(data, mapping, url, webMediaType);
+    }
     return getSerializerForMIMETypeID(id);
 }
 
diff --git a/libraries/hfm/src/hfm/HFMFormatRegistry.h b/libraries/hfm/src/hfm/HFMFormatRegistry.h
index 6e0bd5c66c..6a16dce0b9 100644
--- a/libraries/hfm/src/hfm/HFMFormatRegistry.h
+++ b/libraries/hfm/src/hfm/HFMFormatRegistry.h
@@ -18,7 +18,7 @@
 
 namespace hfm {
 
-class FormatRegistry : public ReadWriteLockable {
+class FormatRegistry {
 public:
     using MIMETypeID = MIMETypeLibrary::ID;
     static const MIMETypeID INVALID_MIME_TYPE_ID { MIMETypeLibrary::INVALID_ID };
@@ -31,6 +31,7 @@ public:
 
 protected:
     MIMETypeLibrary _mimeTypeLibrary;
+    std::mutex _libraryLock;
     class SupportedFormat {
     public:
         SupportedFormat(const MIMETypeID& mimeTypeID, std::unique_ptr<Serializer::Factory>& factory) :
diff --git a/libraries/model-networking/src/model-networking/ModelFormatRegistry.cpp b/libraries/model-networking/src/model-networking/ModelFormatRegistry.cpp
index ccc89eb402..8adc4ea5d9 100644
--- a/libraries/model-networking/src/model-networking/ModelFormatRegistry.cpp
+++ b/libraries/model-networking/src/model-networking/ModelFormatRegistry.cpp
@@ -27,9 +27,10 @@ void ModelFormatRegistry::addDefaultFormats() {
 
 void ModelFormatRegistry::addFormat(const std::shared_ptr<hfm::Format>& format) {
     format->registerFormat(*this);
-    withWriteLock([&](){
+    {
+        std::lock_guard<std::mutex> lock(_formatsLock);
         formats.push_back(format);
-    });
+    }
 }
 
 ModelFormatRegistry::~ModelFormatRegistry() {
diff --git a/libraries/model-networking/src/model-networking/ModelFormatRegistry.h b/libraries/model-networking/src/model-networking/ModelFormatRegistry.h
index becc53fc1b..c88873eaca 100644
--- a/libraries/model-networking/src/model-networking/ModelFormatRegistry.h
+++ b/libraries/model-networking/src/model-networking/ModelFormatRegistry.h
@@ -24,6 +24,7 @@ public:
 protected:
     void addDefaultFormats();
     std::vector<std::shared_ptr<hfm::Format>> formats;
+    std::mutex _formatsLock;
 };
 
 #endif // hifi_ModelFormatRegistry_h