diff --git a/test/src/mbgl/test/stub_file_source.cpp b/test/src/mbgl/test/stub_file_source.cpp
index 7891d5d907d..0bbff84ff32 100644
--- a/test/src/mbgl/test/stub_file_source.cpp
+++ b/test/src/mbgl/test/stub_file_source.cpp
@@ -17,7 +17,12 @@ class StubFileRequest : public AsyncRequest {
     StubFileSource& fileSource;
 };
 
-StubFileSource::StubFileSource() {
+StubFileSource::StubFileSource(ResponseType type_)
+        : type(type_) {
+    if (type == ResponseType::Synchronous) {
+        return;
+    }
+
     timer.start(1ms, 1ms, [this] {
         // Explicit copy to avoid iterator invalidation if ~StubFileRequest gets called within the loop.
         auto pending_ = pending;
@@ -46,7 +51,14 @@ StubFileSource::~StubFileSource() = default;
 
 std::unique_ptr<AsyncRequest> StubFileSource::request(const Resource& resource, Callback callback) {
     auto req = std::make_unique<StubFileRequest>(*this);
-    pending.emplace(req.get(), std::make_tuple(resource, response, callback));
+    if (type == ResponseType::Synchronous) {
+        optional<Response> res = response(resource);
+        if (res) {
+            callback(*res);
+        }
+    } else {
+        pending.emplace(req.get(), std::make_tuple(resource, response, callback));
+    }
     return std::move(req);
 }
 
diff --git a/test/src/mbgl/test/stub_file_source.hpp b/test/src/mbgl/test/stub_file_source.hpp
index 85118e1a777..6cee8377c69 100644
--- a/test/src/mbgl/test/stub_file_source.hpp
+++ b/test/src/mbgl/test/stub_file_source.hpp
@@ -9,7 +9,12 @@ namespace mbgl {
 
 class StubFileSource : public FileSource {
 public:
-    StubFileSource();
+    enum class ResponseType {
+        Asynchronous = 0,
+        Synchronous
+    };
+
+    StubFileSource(ResponseType = ResponseType::Asynchronous);
     ~StubFileSource() override;
 
     std::unique_ptr<AsyncRequest> request(const Resource&, Callback) override;
@@ -36,6 +41,7 @@ class StubFileSource : public FileSource {
     optional<Response> defaultResponse(const Resource&);
 
     std::unordered_map<AsyncRequest*, std::tuple<Resource, ResponseFunction, Callback>> pending;
+    ResponseType type;
     util::Timer timer;
 };
 
diff --git a/test/text/glyph_loader.test.cpp b/test/text/glyph_loader.test.cpp
index be197ebb462..20ac0459251 100644
--- a/test/text/glyph_loader.test.cpp
+++ b/test/text/glyph_loader.test.cpp
@@ -214,3 +214,52 @@ TEST(GlyphManager, LoadingInvalid) {
             {{{"Test Stack"}}, {u'A', u'E'}}
         });
 }
+
+TEST(GlyphManager, ImmediateFileSource) {
+    class GlyphManagerTestSynchronous {
+    public:
+        util::RunLoop loop;
+        StubFileSource fileSource = { StubFileSource::ResponseType::Synchronous };
+        StubGlyphManagerObserver observer;
+        StubGlyphRequestor requestor;
+        GlyphManager glyphManager { fileSource };
+
+        void run(const std::string& url, GlyphDependencies dependencies) {
+            // Squelch logging.
+            Log::setObserver(std::make_unique<Log::NullObserver>());
+
+            glyphManager.setURL(url);
+            glyphManager.setObserver(&observer);
+            glyphManager.getGlyphs(requestor, std::move(dependencies));
+
+            loop.run();
+        }
+
+        void end() {
+            loop.stop();
+        }
+    };
+
+    GlyphManagerTestSynchronous test;
+
+    test.fileSource.glyphsResponse = [&] (const Resource&) {
+        Response response;
+        response.data = std::make_shared<std::string>(util::read_file("test/fixtures/resources/glyphs.pbf"));
+        return response;
+    };
+
+    test.observer.glyphsError = [&] (const FontStack&, const GlyphRange&, std::exception_ptr) {
+        FAIL();
+        test.end();
+    };
+
+    test.requestor.glyphsAvailable = [&] (GlyphMap) {
+        test.end();
+    };
+
+    test.run(
+        "test/fixtures/resources/glyphs.pbf",
+        GlyphDependencies {
+            {{{"Test Stack"}}, {u'a', u'å', u' '}}
+        });
+}