diff --git a/libretro-build-common.sh b/libretro-build-common.sh
index e26b97d0..36b1940f 100755
--- a/libretro-build-common.sh
+++ b/libretro-build-common.sh
@@ -258,7 +258,7 @@ libretro_build_core() {
 	echo "$(color 34)=== $(color 1)$core_name$(color)"
 
 	eval "core_build_rule=\$libretro_${1}_build_rule"
-	[ -z "$core_build_rule" ] && core_build_rule=build_makefile
+	[ -z "$core_build_rule" ] && core_build_rule=generic_makefile
 
 	eval "core_dir=\$libretro_${1}_dir"
 	[ -z "$core_dir" ] && core_dir="libretro-$1"
@@ -285,7 +285,7 @@ libretro_build_core() {
 	fi
 
 	case "$core_build_rule" in
-		build_makefile)
+		generic_makefile)
 			eval "core_build_makefile=\$libretro_${1}_build_makefile"
 			eval "core_build_subdir=\$libretro_${1}_build_subdir"
 
@@ -296,6 +296,9 @@ libretro_build_core() {
 			echo "Building ${1}..."
 			$core_build_rule $1
 
+			;;
+		none)
+			echo "Don't have a build rule for $1, skipping..."
 			;;
 		*)
 			echo "libretro_build_core:Unknown build rule for $1: \"$core_build_rule\"."
diff --git a/rules.d/core-rules.sh b/rules.d/core-rules.sh
index e9542687..bb468ae0 100644
--- a/rules.d/core-rules.sh
+++ b/rules.d/core-rules.sh
@@ -2,6 +2,7 @@
 
 libretro_bsnes_name="bsnes/higan"
 libretro_bsnes_git_url="https://github.com/libretro/bsnes-libretro.git"
+libretro_bsnes_build_rule=none
 # NEED CUSTOM RULE: bsnes
 
 libretro_snes9x_name="SNES9x"
@@ -39,6 +40,7 @@ libretro_handy_git_url="https://github.com/libretro/libretro-handy.git"
 
 libretro_bnes_name="bnes/higan"
 libretro_bnes_git_url="https://github.com/libretro/bnes-libretro.git"
+libretro_bnes_build_rule=none
 # NEED CUSTOM RULE: bnes
 
 libretro_fceumm_name="FCEUmm"
@@ -150,10 +152,12 @@ libretro_mame078_git_url="https://github.com/libretro/mame2003-libretro.git"
 
 libretro_mame139_name="MAME 2010 (0.139)"
 libretro_mame139_git_url="https://github.com/libretro/mame2010-libretro.git"
+libretro_mame139_build_rule=none
 # NEED A BUILD RULE: mame139
 
 libretro_mame_name="MAME (git)"
 libretro_mame_git_url="https://github.com/libretro/mame.git"
+libretro_mame_build_rule=none
 # NEED CUSTOM RULE: mame
 
 libretro_ffmpeg_name="FFmpeg"
@@ -163,10 +167,12 @@ libretro_ffmpeg_build_opengl="optional"
 
 libretro_bsnes_cplusplus98_name="bsnes C++98 (v0.85)"
 libretro_bsnes_cplusplus98_git_url="https://github.com/libretro/bsnes-libretro-cplusplus98.git"
+libretro_bsnes_cplusplus98_build_rule=none
 # NEED CUSTOM RULE: bsnes_cplusplus98
 
 libretro_bsnes_mercury_name="bsnes-mercury"
 libretro_bsnes_mercury_git_url="https://github.com/libretro/bsnes-mercury.git"
+libretro_bsnes_mercury_build_rule=none
 # NEED CUSTOM RULE: bsnes_mercury
 
 libretro_picodrive_name="Picodrive"
@@ -180,6 +186,7 @@ libretro_tgbdual_git_url="https://github.com/libretro/tgbdual-libretro.git"
 
 libretro_mupen64plus_name="Mupen64Plus"
 libretro_mupen64plus_git_url="https://github.com/libretro/mupen64plus-libretro.git"
+libretro_mupen64plus_build_rule=none
 # NEED CUSTOM RULE: mupen64plus
 
 libretro_dinothawr_name="Dinothawr"
@@ -188,6 +195,7 @@ libretro_dinothawr_build_platform="$FORMAT_COMPILER_TARGET_ALT"
 
 libretro_uae_name="UAE"
 libretro_uae_git_url="https://github.com/libretro/libretro-uae.git"
+libretro_uae_build_rule=none
 # NEED A BUILD RULE: uae
 
 libretro_3dengine_name="3DEngine"
@@ -196,6 +204,7 @@ libretro_3dengine_build_opengl=yes
 
 libretro_remotejoy_name="RemoteJoy"
 libretro_remotejoy_git_url="https://github.com/libretro/libretro-remotejoy.git"
+libretro_remotejoy_build_rule=none
 # NEED A BUILD RULE: remotejoy
 
 libretro_bluemsx_name="blueMSX"
@@ -246,6 +255,7 @@ libretro_hatari_build_makefile="Makefile.libretro"
 
 libretro_tempgba_name="TempGBA"
 libretro_tempgba_git_url="https://github.com/libretro/TempGBA-libretro.git"
+libretro_tempgba_build_rule=none
 # NEED A BUILD RULE: tempgba
 
 libretro_gpsp_name="gpSP"
@@ -254,6 +264,7 @@ libretro_gpsp_git_url="https://github.com/libretro/gpsp.git"
 
 libretro_emux_name="Emux"
 libretro_emux_git_url="https://github.com/libretro/emux.git"
+libretro_emux_build_rule=none
 # NEED CUSTOM RULE: emux
 
 libretro_fuse_name="Fuse"