diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index a5142216..55ec218d 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -16,7 +16,7 @@ jobs:
         uses: actions/checkout@master
         with:
           path: rgbds
-          ref: v0.8.0
+          ref: v0.9.0
           repository: gbdev/rgbds
 
       - name: Install rgbds
diff --git a/INSTALL.md b/INSTALL.md
index aa5874db..9b5968c6 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -42,9 +42,9 @@ Run setup and leave the default settings. At the "**Select Packages**" step, cho
 
 Double click on the text that says "**Skip**" next to each package to select the most recent version to install.
 
-Then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#pre-built) for Windows with Cygwin to install **rgbds 0.7.0**.
+Then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#pre-built) for Windows with Cygwin to install **rgbds 0.9.0**.
 
-**Note:** If you already have an installed rgbds older than 0.7.0, you will need to update to 0.7.0. Ignore this if you have never installed rgbds before. If a version newer than 0.7.0 does not work, try downloading 0.7.0.
+**Note:** If you already have an installed rgbds older than 0.9.0, you will need to update to 0.9.0. Ignore this if you have never installed rgbds before. If a version newer than 0.9.0 does not work, try downloading 0.9.0.
 
 Now open the **Cygwin terminal** and enter the following commands.
 
@@ -67,7 +67,7 @@ Install [**Homebrew**](https://brew.sh/). Follow the official instructions.
 
 Open **Terminal** and prepare to enter commands.
 
-Then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#pre-built) for macOS to install **rgbds 0.7.0**.
+Then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#pre-built) for macOS to install **rgbds 0.9.0**.
 
 Now you're ready to [build **pokegold**](#build-pokegold).
 
@@ -84,7 +84,7 @@ To install the software required for **pokegold**:
 sudo apt-get install make gcc git
 ```
 
-Then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.7.0** from source.
+Then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.9.0** from source.
 
 ### OpenSUSE
 
@@ -94,7 +94,7 @@ To install the software required for **pokegold**:
 sudo zypper install make gcc git
 ```
 
-Then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.7.0** from source.
+Then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.9.0** from source.
 
 ### Arch Linux
 
@@ -104,7 +104,7 @@ To install the software required for **pokegold**:
 sudo pacman -S make gcc git rgbds
 ```
 
-If you want to compile and install **rgbds** yourself instead, then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.7.0** from source.
+If you want to compile and install **rgbds** yourself instead, then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.9.0** from source.
 
 ### Termux
 
@@ -120,7 +120,7 @@ To install **rgbds**:
 pkg install rgbds
 ```
 
-If you want to compile and install **rgbds** yourself instead, then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.7.0** from source.
+If you want to compile and install **rgbds** yourself instead, then follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.9.0** from source.
 
 ### Other distros
 
@@ -131,7 +131,7 @@ If your distro is not listed here, try to find the required software in its repo
 - `git`
 - `rgbds`
 
-If `rgbds` is not available, you'll need to follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.7.0** from source.
+If `rgbds` is not available, you'll need to follow the [**rgbds** instructions](https://rgbds.gbdev.io/install#building-from-source) to build **rgbds 0.9.0** from source.
 
 Now you're ready to [build **pokegold**](#build-pokegold).
 
@@ -165,12 +165,12 @@ make
 
 ### Build with a local rgbds version
 
-If you have different projects that require different versions of `rgbds`, it might not be convenient to install rgbds 0.7.0 globally. Instead, you can put its files in a directory within pokegold, such as `pokegold/rgbds-0.7.0/`. Then specify it when you run `make`:
+If you have different projects that require different versions of `rgbds`, it might not be convenient to install rgbds 0.9.0 globally. Instead, you can put its files in a directory within pokegold, such as `pokegold/rgbds-0.9.0/`. Then specify it when you run `make`:
 
 ```bash
-make RGBDS=rgbds-0.7.0/ gold
+make RGBDS=rgbds-0.9.0/ gold
 ```
 
 ```bash
-make RGBDS=rgbds-0.7.0/ silver
+make RGBDS=rgbds-0.9.0/ silver
 ```
diff --git a/Makefile b/Makefile
index 1a85a00a..fc9ac0b7 100644
--- a/Makefile
+++ b/Makefile
@@ -107,7 +107,7 @@ tools:
 	$(MAKE) -C tools/
 
 
-RGBASMFLAGS = -Q8 -P includes.asm -Weverything -Wnumeric-string=2 -Wtruncation=1
+RGBASMFLAGS = -Q8 -P includes.asm -Weverything -Wtruncation=1
 # Create a sym/map for debug purposes if `make` run with `DEBUG=1`
 ifeq ($(DEBUG),1)
 RGBASMFLAGS += -E
@@ -174,12 +174,12 @@ $(foreach obj, $(silver_vc_excl_obj), \
 endif
 
 
-pokegold_opt         = -cjsv -t POKEMON_GLD -i AAUE -k 01 -l 0x33 -m 0x10 -r 3 -p 0
-pokesilver_opt       = -cjsv -t POKEMON_SLV -i AAXE -k 01 -l 0x33 -m 0x10 -r 3 -p 0
-pokegold_debug_opt   = -cjsv -t POKEMON_GLD -i AAUE -k 01 -l 0x33 -m 0x10 -r 3 -p 0
-pokesilver_debug_opt = -cjsv -t POKEMON_SLV -i AAXE -k 01 -l 0x33 -m 0x10 -r 3 -p 0
-pokegold_vc_opt      = -cjsv -t POKEMON_GLD -i AAUE -k 01 -l 0x33 -m 0x10 -r 3 -p 0
-pokesilver_vc_opt    = -cjsv -t POKEMON_SLV -i AAXE -k 01 -l 0x33 -m 0x10 -r 3 -p 0
+pokegold_opt         = -cjsv -t POKEMON_GLD -i AAUE -k 01 -l 0x33 -m MBC3+TIMER+RAM+BATTERY -r 3 -p 0
+pokesilver_opt       = -cjsv -t POKEMON_SLV -i AAXE -k 01 -l 0x33 -m MBC3+TIMER+RAM+BATTERY -r 3 -p 0
+pokegold_debug_opt   = -cjsv -t POKEMON_GLD -i AAUE -k 01 -l 0x33 -m MBC3+TIMER+RAM+BATTERY -r 3 -p 0
+pokesilver_debug_opt = -cjsv -t POKEMON_SLV -i AAXE -k 01 -l 0x33 -m MBC3+TIMER+RAM+BATTERY -r 3 -p 0
+pokegold_vc_opt      = -cjsv -t POKEMON_GLD -i AAUE -k 01 -l 0x33 -m MBC3+TIMER+RAM+BATTERY -r 3 -p 0
+pokesilver_vc_opt    = -cjsv -t POKEMON_SLV -i AAXE -k 01 -l 0x33 -m MBC3+TIMER+RAM+BATTERY -r 3 -p 0
 
 %.gbc: $$(%_obj) layout.link
 	$(RGBLINK) -n $*.sym -m $*.map -l layout.link -o $@ $(filter %.o,$^)
diff --git a/engine/battle/battle_transition.asm b/engine/battle/battle_transition.asm
index 8881f89a..2a471722 100644
--- a/engine/battle/battle_transition.asm
+++ b/engine/battle/battle_transition.asm
@@ -614,8 +614,7 @@ StartTrainerBattle_LoadPokeBallGraphics:
 
 .PokeBallTransition:
 	; 16x16 overlay of a Poke Ball
-pusho
-opt b.X ; . = 0, X = 1
+pusho b.X ; . = 0, X = 1
 	bigdw %......XXXX......
 	bigdw %....XXXXXXXX....
 	bigdw %..XXXX....XXXX..
diff --git a/engine/pokedex/pokedex.asm b/engine/pokedex/pokedex.asm
index 47949483..26a2b65d 100644
--- a/engine/pokedex/pokedex.asm
+++ b/engine/pokedex/pokedex.asm
@@ -15,8 +15,7 @@
 	const DEXSTATE_UPDATE_UNOWN_MODE
 	const DEXSTATE_EXIT
 
-DEF POKEDEX_SCX EQU 5
-EXPORT POKEDEX_SCX
+EXPORT DEF POKEDEX_SCX EQU 5
 
 Pokedex:
 	ldh a, [hWX]
diff --git a/macros/code.asm b/macros/code.asm
index 6856b1dc..7a10f84d 100644
--- a/macros/code.asm
+++ b/macros/code.asm
@@ -35,17 +35,11 @@ MACRO maskbits
 ; 	cp 26
 ; 	jr nc, .loop
 	assert 0 < (\1) && (\1) <= $100, "bitmask must be 8-bit"
-	DEF x = 1
-	rept 8
-		if x + 1 < (\1)
-			DEF x = (x << 1) | 1
-		endc
-	endr
+	DEF x = (1 << BITWIDTH((\1) - 1)) - 1
 	if _NARG == 2
-		and x << (\2)
-	else
-		and x
+		DEF x <<= \2
 	endc
+	and x
 ENDM
 
 MACRO calc_sine_wave
diff --git a/rgbdscheck.asm b/rgbdscheck.asm
index af2c1155..9b83b685 100644
--- a/rgbdscheck.asm
+++ b/rgbdscheck.asm
@@ -1,6 +1,6 @@
 IF !DEF(__RGBDS_MAJOR__) || !DEF(__RGBDS_MINOR__) || !DEF(__RGBDS_PATCH__)
-	fail "pokegold requires rgbds v0.7.0 or newer."
+	fail "pokegold requires rgbds v0.9.0 or newer."
 ENDC
-IF __RGBDS_MAJOR__ == 0 && __RGBDS_MINOR__ <  7
-	fail "pokegold requires rgbds v0.7.0 or newer."
+IF __RGBDS_MAJOR__ == 0 && __RGBDS_MINOR__ < 9
+	fail "pokegold requires rgbds v0.9.0 or newer."
 ENDC