diff --git a/doomsday/engine/portable/include/gl_defer.h b/doomsday/engine/portable/include/gl_defer.h
index 90e85e0d4e..5ecb1c3acc 100644
--- a/doomsday/engine/portable/include/gl_defer.h
+++ b/doomsday/engine/portable/include/gl_defer.h
@@ -73,8 +73,10 @@ void GL_ReleaseReservedNames(void);
 void GL_DeferTextureUpload(const struct texturecontent_s* content);
 
 // Deferring functions for various function signatures.
-#define LIBDENG_GL_DEFER1(form, x)      void GL_Defer_##form(void (GL_CALL *ptr)(x), x)
-#define LIBDENG_GL_DEFER2(form, x, y)   void GL_Defer_##form(void (GL_CALL* ptr)(x, y), x, y)
+#define LIBDENG_GL_DEFER1(form, x)          void GL_Defer_##form(void (GL_CALL *ptr)(x), x)
+#define LIBDENG_GL_DEFER2(form, x, y)       void GL_Defer_##form(void (GL_CALL* ptr)(x, y), x, y)
+#define LIBDENG_GL_DEFER3(form, x, y, z)    void GL_Defer_##form(void (GL_CALL* ptr)(x, y, z), x, y, z)
+#define LIBDENG_GL_DEFER4(form, x, y, z, w) void GL_Defer_##form(void (GL_CALL* ptr)(x, y, z, w), x, y, z, w)
 
 LIBDENG_GL_DEFER1(e,         GLenum e);
 LIBDENG_GL_DEFER2(uintArray, GLsizei count, const GLuint* values);
diff --git a/doomsday/engine/portable/include/gl_deferredapi.h b/doomsday/engine/portable/include/gl_deferredapi.h
index 6bba4a9300..abe13cd4a1 100644
--- a/doomsday/engine/portable/include/gl_deferredapi.h
+++ b/doomsday/engine/portable/include/gl_deferredapi.h
@@ -5,6 +5,9 @@
  * Redefines GL API functions so that they're replaced with ones that defer the
  * call when needed.
  *
+ * @note  Only the GL API functions declared in this file are safe to call from
+ * outside the main thread!
+ *
  * @authors Copyright © 2012 Jaakko Keränen <jaakko.keranen@iki.fi>
  * @authors Copyright © 2012 Daniel Swanson <danij@dengine.net>
  *
diff --git a/doomsday/engine/portable/src/gl_defer.c b/doomsday/engine/portable/src/gl_defer.c
index 2661f85c8e..f2b8c4194a 100644
--- a/doomsday/engine/portable/src/gl_defer.c
+++ b/doomsday/engine/portable/src/gl_defer.c
@@ -45,10 +45,10 @@ typedef enum {
         DTT_FUNC_PTR_UINT_ARRAY,
     DTT_FUNC_PTR_END,
 
-    DEFERREDTASK_TYPES_COUNT
+    DEFERREDTASK_TYPES_LAST
 } deferredtask_type_t;
 
-#define VALID_DEFERREDTASK_TYPE(t)      ((t) >= DEFERREDTASK_TYPES_FIRST || (t) < DEFERREDTASK_TYPES_COUNT)
+#define VALID_DEFERREDTASK_TYPE(t)      ((t) >= DEFERREDTASK_TYPES_FIRST || (t) < DEFERREDTASK_TYPES_LAST)
 
 typedef struct deferredtask_s {
     struct deferredtask_s* next;
diff --git a/doomsday/engine/portable/src/gl_texmanager.c b/doomsday/engine/portable/src/gl_texmanager.c
index cb9c39c882..c6fa7595de 100644
--- a/doomsday/engine/portable/src/gl_texmanager.c
+++ b/doomsday/engine/portable/src/gl_texmanager.c
@@ -1315,8 +1315,6 @@ void GL_ReleaseSystemTextures(void)
 
     VERBOSE( Con_Message("Releasing System textures...\n") )
 
-    LIBDENG_ASSERT_IN_MAIN_THREAD();
-
     // The rendering lists contain persistent references to texture names.
     // Which, obviously, can't persist any longer...
     RL_DeleteLists();
diff --git a/doomsday/engine/portable/src/rend_particle.c b/doomsday/engine/portable/src/rend_particle.c
index ee8ccb12a6..aa34c102e4 100644
--- a/doomsday/engine/portable/src/rend_particle.c
+++ b/doomsday/engine/portable/src/rend_particle.c
@@ -204,8 +204,6 @@ void Rend_ParticleReleaseSystemTextures(void)
 {
     if(novideo) return;
 
-    LIBDENG_ASSERT_IN_MAIN_THREAD();
-
     glDeleteTextures(1, (const GLuint*) &pointTex);
     pointTex = 0;
 }
@@ -214,8 +212,6 @@ void Rend_ParticleReleaseExtraTextures(void)
 {
     if(novideo) return;
 
-    LIBDENG_ASSERT_IN_MAIN_THREAD();
-
     glDeleteTextures(NUM_TEX_NAMES, (const GLuint*) ptctexname);
     memset(ptctexname, 0, sizeof(ptctexname));
 }
diff --git a/doomsday/engine/portable/src/ui_main.c b/doomsday/engine/portable/src/ui_main.c
index 7ba73b18bd..f2aa8ae68a 100644
--- a/doomsday/engine/portable/src/ui_main.c
+++ b/doomsday/engine/portable/src/ui_main.c
@@ -291,8 +291,6 @@ void UI_LoadTextures(void)
 
 void UI_ReleaseTextures(void)
 {
-    LIBDENG_ASSERT_IN_MAIN_THREAD();
-
     glDeleteTextures(NUM_UITEXTURES, (const GLuint*) uiTextures);
     memset(uiTextures, 0, sizeof(uiTextures));
 }