diff --git a/dlls/wined3d/context_gl.c b/dlls/wined3d/context_gl.c
index 8217d04686c..b82849f8470 100644
--- a/dlls/wined3d/context_gl.c
+++ b/dlls/wined3d/context_gl.c
@@ -2778,9 +2778,12 @@ static void *wined3d_allocator_chunk_gl_map(struct wined3d_allocator_chunk_gl *c
         struct wined3d_context_gl *context_gl)
 {
     const struct wined3d_gl_info *gl_info = context_gl->gl_info;
+    void *map_ptr;
 
     TRACE("chunk %p, gl_buffer %u, map_ptr %p.\n", chunk_gl, chunk_gl->gl_buffer, chunk_gl->c.map_ptr);
 
+    wined3d_allocator_chunk_gl_lock(chunk_gl);
+
     if (!chunk_gl->c.map_ptr)
     {
         unsigned int flags = wined3d_device_gl_get_memory_type_flags(chunk_gl->memory_type) & ~GL_CLIENT_STORAGE_BIT;
@@ -2795,6 +2798,7 @@ static void *wined3d_allocator_chunk_gl_map(struct wined3d_allocator_chunk_gl *c
                 0, WINED3D_ALLOCATOR_CHUNK_SIZE, flags));
         if (!chunk_gl->c.map_ptr)
         {
+            wined3d_allocator_chunk_gl_unlock(chunk_gl);
             ERR("Failed to map chunk memory.\n");
             return NULL;
         }
@@ -2803,8 +2807,11 @@ static void *wined3d_allocator_chunk_gl_map(struct wined3d_allocator_chunk_gl *c
     }
 
     ++chunk_gl->c.map_count;
+    map_ptr = chunk_gl->c.map_ptr;
 
-    return chunk_gl->c.map_ptr;
+    wined3d_allocator_chunk_gl_unlock(chunk_gl);
+
+    return map_ptr;
 }
 
 static void wined3d_allocator_chunk_gl_unmap(struct wined3d_allocator_chunk_gl *chunk_gl,
@@ -2814,14 +2821,18 @@ static void wined3d_allocator_chunk_gl_unmap(struct wined3d_allocator_chunk_gl *
 
     TRACE("chunk_gl %p, context_gl %p.\n", chunk_gl, context_gl);
 
-    if (--chunk_gl->c.map_count)
-        return;
+    wined3d_allocator_chunk_gl_lock(chunk_gl);
 
-    wined3d_context_gl_bind_bo(context_gl, GL_PIXEL_UNPACK_BUFFER, chunk_gl->gl_buffer);
-    GL_EXTCALL(glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER));
-    chunk_gl->c.map_ptr = NULL;
+    if (!--chunk_gl->c.map_count)
+    {
+        wined3d_context_gl_bind_bo(context_gl, GL_PIXEL_UNPACK_BUFFER, chunk_gl->gl_buffer);
+        GL_EXTCALL(glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER));
+        chunk_gl->c.map_ptr = NULL;
 
-    adapter_adjust_mapped_memory(context_gl->c.device->adapter, -WINED3D_ALLOCATOR_CHUNK_SIZE);
+        adapter_adjust_mapped_memory(context_gl->c.device->adapter, -WINED3D_ALLOCATOR_CHUNK_SIZE);
+    }
+
+    wined3d_allocator_chunk_gl_unlock(chunk_gl);
 }
 
 static void *wined3d_bo_gl_map(struct wined3d_bo_gl *bo, struct wined3d_context_gl *context_gl, uint32_t flags)
diff --git a/dlls/wined3d/device.c b/dlls/wined3d/device.c
index 9488e8c642e..f163e77fcf1 100644
--- a/dlls/wined3d/device.c
+++ b/dlls/wined3d/device.c
@@ -993,14 +993,13 @@ static struct wined3d_allocator_chunk *wined3d_allocator_gl_create_chunk(struct
 
 static void wined3d_allocator_gl_destroy_chunk(struct wined3d_allocator_chunk *chunk)
 {
+    struct wined3d_device_gl *device_gl = wined3d_device_gl_from_allocator(chunk->allocator);
     struct wined3d_allocator_chunk_gl *chunk_gl = wined3d_allocator_chunk_gl(chunk);
     const struct wined3d_gl_info *gl_info;
     struct wined3d_context_gl *context_gl;
-    struct wined3d_device_gl *device_gl;
 
     TRACE("chunk %p.\n", chunk);
 
-    device_gl = CONTAINING_RECORD(chunk_gl->c.allocator, struct wined3d_device_gl, allocator);
     context_gl = wined3d_context_gl(context_acquire(&device_gl->d, NULL, 0));
     gl_info = context_gl->gl_info;
 
diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index 96ce75fbb58..c8c9bb7c8c6 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -4213,6 +4213,11 @@ static inline struct wined3d_device_gl *wined3d_device_gl(struct wined3d_device
     return CONTAINING_RECORD(device, struct wined3d_device_gl, d);
 }
 
+static inline struct wined3d_device_gl *wined3d_device_gl_from_allocator(struct wined3d_allocator *allocator)
+{
+    return CONTAINING_RECORD(allocator, struct wined3d_device_gl, allocator);
+}
+
 static inline void wined3d_device_gl_allocator_lock(struct wined3d_device_gl *device_gl)
 {
     EnterCriticalSection(&device_gl->allocator_cs);
@@ -4223,6 +4228,16 @@ static inline void wined3d_device_gl_allocator_unlock(struct wined3d_device_gl *
     LeaveCriticalSection(&device_gl->allocator_cs);
 }
 
+static inline void wined3d_allocator_chunk_gl_lock(struct wined3d_allocator_chunk_gl *chunk_gl)
+{
+    wined3d_device_gl_allocator_lock(wined3d_device_gl_from_allocator(chunk_gl->c.allocator));
+}
+
+static inline void wined3d_allocator_chunk_gl_unlock(struct wined3d_allocator_chunk_gl *chunk_gl)
+{
+    wined3d_device_gl_allocator_unlock(wined3d_device_gl_from_allocator(chunk_gl->c.allocator));
+}
+
 bool wined3d_device_gl_create_bo(struct wined3d_device_gl *device_gl,
         struct wined3d_context_gl *context_gl, GLsizeiptr size, GLenum binding,
         GLenum usage, bool coherent, GLbitfield flags, struct wined3d_bo_gl *bo) DECLSPEC_HIDDEN;