diff --git a/Makefile b/Makefile
index 393c4e6..9b67a5e 100644
--- a/Makefile
+++ b/Makefile
@@ -30,20 +30,32 @@ ifeq ($(PARENT_OUTPUT_DIR),.)
 endif
 
 # Find the N64 toolchain, for creating object files.
+ifneq (, $(shell which mips64-linux-gnuabi64-as))
+  AS := mips64-linux-gnuabi64-as
+else
 ifneq (, $(shell which mips64-linux-gnu-as))
   AS := mips64-linux-gnu-as
 else
 ifneq (, $(shell which mips64-ultra-elf-as))
   AS := mips64-ultra-elf-as
 else
+ifneq (, $(shell which mips64-elf-as))
+  AS := mips64-elf-as
+else
 ifneq (, $(shell which mips64-as))
   AS := mips64-as
+else
+ifneq (, $(shell which mips-linux-gnu-as))
+  AS := mips-linux-gnu-as
 else
   $(warning Could not find N64 linker, not building object files)
   AS := 
 endif
 endif
 endif
+endif
+endif
+endif
 
 NO_COL := \033[0m
 RED    := \033[0;31m
diff --git a/docs/Documentation/Porting your Romhack.md b/docs/Documentation/Porting your Romhack.md
index f42e36b..3a7c6db 100644
--- a/docs/Documentation/Porting your Romhack.md	
+++ b/docs/Documentation/Porting your Romhack.md	
@@ -37,6 +37,13 @@ similar for other games):
 
 Both OoT and SM64:
 
+- In any place where your game creates a viewport (whether statically or
+  dynamically) (search for `Vp` case-sensitive, `SPViewport`, and `G_MAXZ`),
+  change the maximum Z value from `G_MAXZ` to `G_NEW_MAXZ` and negate the
+  Y scale. For more information, see the comment next to `G_MAXZ` in the GBI.
+  Note that your romhack codebase may have the constant hardcoded, usually as
+  `511` which is supposed to be `(G_MAXZ/2)`, instead of actually writing
+  `G_MAXZ`; you need to change these too, there are several of these in SM64.
 - Remove uses of internal GBI features which have been removed in F3DEX3 (see
   @ref compatibility for full list). In OoT, the only changes needed are:
     - In `src/code/ucode_disas.c`, remove the switch statement cases for
diff --git a/f3dex3.s b/f3dex3.s
index 051542c..f35cd74 100644
--- a/f3dex3.s
+++ b/f3dex3.s
@@ -2806,6 +2806,7 @@ G_POPMTX_handler:
     lw      $2, OSTask + OSTask_dram_stack  // Top of the stack
     sub     cmd_w1_dram, $11, cmd_w1_dram   // Decrease pointer by amount in command
     sub     $1, cmd_w1_dram, $2             // Is it still valid / within the stack?
+    sb      $zero, dirLightsXfrmValid       // Mark lights as needing recompute
     bgez    $1, @@skip                      // If so, skip the failsafe
      sh     $zero, mvpValid                 // and dirLightsXfrmValid; mark both mtx and dir lts invalid
     move    cmd_w1_dram, $2                 // Use the top of the stack as the new pointer
diff --git a/gbi.h b/gbi.h
index 69fc7de..9cdf737 100644
--- a/gbi.h
+++ b/gbi.h
@@ -16,10 +16,20 @@
 #ifndef F3DEX3_H
 #define F3DEX3_H
 
+/* Don't remove this line which defines F3DEX3 as F3DEX2. Other headers in your
+romhack codebase will likely assume that if the microcode is not F3DEX2, it is
+F3DEX1 or older, thus breaking F3DEX3 compatibility even more. */
 #define F3DEX_GBI_2  1
 #define F3DEX_GBI_PL 1
 #define F3DEX_GBI_3  1
 
+/* This is only included to check correctness of OS_YIELD_DATA_SIZE. If you are
+sure this is correct in your project, you can remove this include. */
+#include "ultra64/sptask.h"
+#if OS_YIELD_DATA_SIZE != 0xC00
+#error "F3DEX3 requires OS_YIELD_DATA_SIZE == 0xC00"
+#endif
+
 #ifdef REQUIRE_SEMICOLONS_AFTER_GBI_COMMANDS
 /* OoT style, semicolons required after using macros, cleaner code. If modding
 SM64, will have to fix a few places the codebase omits the semicolons. */