diff --git a/MapboxSceneKit/MapboxImageAPI.swift b/MapboxSceneKit/MapboxImageAPI.swift
index bb595d2..b672ab6 100644
--- a/MapboxSceneKit/MapboxImageAPI.swift
+++ b/MapboxSceneKit/MapboxImageAPI.swift
@@ -113,7 +113,10 @@ public final class MapboxImageAPI: NSObject {
 
         let group = DispatchGroup()
         let groupID = UUID()
-        pendingFetches[groupID] = [UUID]()
+        self.pendingFetchesDispatchQueue.sync(flags: .barrier) { [weak self] in
+            guard let self = self else { return }
+            self.pendingFetches[groupID] = [UUID]()
+        }
 
         var completed: Int = 0
         let total = bounding.xs.count * bounding.ys.count
@@ -196,7 +199,10 @@ public final class MapboxImageAPI: NSObject {
 
         let group = DispatchGroup()
         let groupID = UUID()
-        pendingFetches[groupID] = [UUID]()
+        pendingFetchesDispatchQueue.sync(flags: .barrier) { [weak self] in
+            guard let self = self else { return }
+            self.pendingFetches[groupID] = [UUID]()
+        }
 
         var completed: Int = 0
         let total = bounding.xs.count * bounding.ys.count
@@ -236,7 +242,10 @@ public final class MapboxImageAPI: NSObject {
         }
 
         group.notify(queue: DispatchQueue.main) {
-            self.pendingFetches.removeValue(forKey: groupID)
+            self.pendingFetchesDispatchQueue.sync(flags: .barrier) { [weak self] in
+                guard let self = self else { return }
+                self.pendingFetches.removeValue(forKey: groupID)
+            }
             completion(error == nil ? imageBuilder.makeImage() : nil, error?.toNSError())
         }
 
@@ -248,13 +257,16 @@ public final class MapboxImageAPI: NSObject {
      **/
     @objc
     func cancelRequestWithID(_ groupID: UUID) {
-        guard let tasks = pendingFetches[groupID] else {
-            return
-        }
-        for task in tasks {
-            httpAPI.cancelRequestWithID(task)
+        self.pendingFetchesDispatchQueue.sync(flags: .barrier) { [weak self] in
+            guard let tasks = pendingFetches[groupID] else {
+                return
+            }
+            for task in tasks {
+                httpAPI.cancelRequestWithID(task)
+            }
+
+            self?.pendingFetches.removeValue(forKey: groupID)
         }
-        pendingFetches.removeValue(forKey: groupID)
     }
 
     //MARK: - Helpers
diff --git a/MapboxSceneKit/Tile Fetching/MapboxHTTPAPI.swift b/MapboxSceneKit/Tile Fetching/MapboxHTTPAPI.swift
index a4882c5..e46d528 100644
--- a/MapboxSceneKit/Tile Fetching/MapboxHTTPAPI.swift	
+++ b/MapboxSceneKit/Tile Fetching/MapboxHTTPAPI.swift	
@@ -26,9 +26,10 @@ enum FetchError: Int {
 }
 
 internal final class MapboxHTTPAPI {
+    private static var tileDownloadTaskDispatchQueue = DispatchQueue(label: "com.mapbox.scenekit.api", attributes: [.concurrent])
     private static var operationQueue: OperationQueue = {
         var operationQueue = OperationQueue()
-        operationQueue.underlyingQueue = DispatchQueue(label: "com.mapbox.scenekit.api", attributes: [.concurrent])
+        operationQueue.underlyingQueue = tileDownloadTaskDispatchQueue
         operationQueue.name = "Mapbox API Queue"
         operationQueue.maxConcurrentOperationCount = 10
         return operationQueue