diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index 661718eb4..98645c296 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -1,4 +1,5 @@
 May 31, 2009  (Changes by Graf Zahl)
+- Added Gez's AMMO_CHECKBOTH submission.
 - Added Gez's THRUSPECIES submission.
 - Added loading directories into the lump directory.
 - fixed: The Dehacked parser could not parse flag values with the highest bit
diff --git a/src/g_shared/a_pickups.h b/src/g_shared/a_pickups.h
index 58709d97f..99a77bdaf 100644
--- a/src/g_shared/a_pickups.h
+++ b/src/g_shared/a_pickups.h
@@ -316,7 +316,7 @@ enum
 	WIF_ALT_USES_BOTH =		0x00000100, // alternate fire uses both ammo
 	WIF_WIMPY_WEAPON =		0x00000200, // change away when ammo for another weapon is replenished
 	WIF_POWERED_UP =		0x00000400, // this is a tome-of-power'ed version of its sister
-
+	WIF_AMMO_CHECKBOTH =	0x00000800, // check for both primary and secondary fire before switching it off
 	WIF_NO_AUTO_SWITCH =	0x00001000,	// never switch to this weapon when it's picked up
 	WIF_STAFF2_KICKBACK =	0x00002000, // the powered-up Heretic staff has special kickba
 
diff --git a/src/g_shared/a_weapons.cpp b/src/g_shared/a_weapons.cpp
index 8beec1688..af650a0f2 100644
--- a/src/g_shared/a_weapons.cpp
+++ b/src/g_shared/a_weapons.cpp
@@ -438,7 +438,7 @@ bool AWeapon::CheckAmmo (int fireMode, bool autoSwitch, bool requireAmmo)
 	{ // If this weapon has no alternate fire, then there is never enough ammo for it
 		enough &= 1;
 	}
-	if ((enough & enoughmask) == enoughmask)
+	if (((enough & enoughmask) == enoughmask) || (enough && (WeaponFlags & WIF_AMMO_CHECKBOTH)))
 	{
 		return true;
 	}
diff --git a/src/thingdef/thingdef_data.cpp b/src/thingdef/thingdef_data.cpp
index c1d91d618..0a199aeb3 100644
--- a/src/thingdef/thingdef_data.cpp
+++ b/src/thingdef/thingdef_data.cpp
@@ -277,6 +277,7 @@ static FFlagDef WeaponFlags[] =
 	DEFINE_FLAG(WIF_BOT, BFG, AWeapon, WeaponFlags),
 	DEFINE_FLAG(WIF, CHEATNOTWEAPON, AWeapon, WeaponFlags),
 	DEFINE_FLAG(WIF, NO_AUTO_SWITCH, AWeapon, WeaponFlags),
+	DEFINE_FLAG(WIF, AMMO_CHECKBOTH, AWeapon, WeaponFlags),
 	
 	DEFINE_DUMMY_FLAG(NOLMS),
 };