diff --git a/build-config.sh b/build-config.sh
index ec1603a9..f23b6124 100644
--- a/build-config.sh
+++ b/build-config.sh
@@ -34,6 +34,9 @@ include_core_genesis_plus_gx
 include_core_picodrive
 include_core_blastem
 
+# --- Master System cores ---
+include_core_gearsystem
+
 # --- Arcade emulator cores ---
 include_core_fbalpha
 include_core_fbalpha2012
diff --git a/rules.d/core-rules.sh b/rules.d/core-rules.sh
index 436df39a..8afe1901 100644
--- a/rules.d/core-rules.sh
+++ b/rules.d/core-rules.sh
@@ -348,6 +348,15 @@ libretro_gearboy_build_platform="$FORMAT_COMPILER_TARGET_ALT"
 libretro_gearboy_build_subdir="platforms/libretro"
 libretro_gearboy_build_makefile="Makefile"
 
+include_core_gearsystem() {
+   register_module core "gearsystem"
+}
+libretro_gearsystem_name="Gearsystem"
+libretro_gearsystem_git_url="https://github.com/drhelius/Gearsystem.git"
+libretro_gearsystem_build_platform="$FORMAT_COMPILER_TARGET_ALT"
+libretro_gearsystem_build_subdir="platforms/libretro"
+libretro_gearsystem_build_makefile="Makefile"
+
 include_core_sameboy() {
 	register_module core "sameboy"
 }