diff --git a/core/ExtensionSys.cpp b/core/ExtensionSys.cpp
index 146bb168..9212a3bb 100644
--- a/core/ExtensionSys.cpp
+++ b/core/ExtensionSys.cpp
@@ -73,6 +73,8 @@ CLocalExtension::CLocalExtension(const char *filename)
 		"extensions/auto.2.l4d/%s",
 #elif SOURCE_ENGINE == SE_ORANGEBOX
 		"extensions/auto.2.ep2/%s",
+#elif SOURCE_ENGINE == SE_ORANGEBOXVALVE
+		"extensions/auto.2.ep2valve",
 #elif SOURCE_ENGINE == SE_DARKMESSIAH
 		"extensions/auto.2.darkm/%s",
 #else
diff --git a/core/GameConfigs.cpp b/core/GameConfigs.cpp
index a4509961..cd7f540a 100644
--- a/core/GameConfigs.cpp
+++ b/core/GameConfigs.cpp
@@ -109,6 +109,8 @@ static bool DoesEngineMatch(const char *value)
 	if (strcmp(value, "darkmessiah") == 0)
 #elif SOURCE_ENGINE == SE_ORANGEBOX
 	if (strcmp(value, "orangebox") == 0)
+#elif SOURCE_ENGINE == SE_ORANGEBOXVALVE
+	if (strcmp(value, "orangebox_valve") == 0)
 #elif SOURCE_ENGINE == SE_LEFT4DEAD
 	if (strcmp(value, "left4dead") == 0)
 #else
diff --git a/core/PluginSys.h b/core/PluginSys.h
index d40cff17..df6a872e 100644
--- a/core/PluginSys.h
+++ b/core/PluginSys.h
@@ -49,7 +49,7 @@
 #include <IRootConsoleMenu.h>
 #if SOURCE_ENGINE == SE_LEFT4DEAD
 #include "convar_sm_l4d.h"
-#elif SOURCE_ENGINE == SE_ORANGEBOX
+#elif (SOURCE_ENGINE == SE_ORANGEBOX) || (SOURCE_ENGINE == SE_ORANGEBOXVALVE)
 #include "convar_sm_ob.h"
 #else
 #include "convar_sm.h"
diff --git a/core/sourcemm_api.h b/core/sourcemm_api.h
index 2f0f04dd..d4fb095a 100644
--- a/core/sourcemm_api.h
+++ b/core/sourcemm_api.h
@@ -34,7 +34,7 @@
 
 #if SOURCE_ENGINE == SE_LEFT4DEAD
 #include "convar_sm_l4d.h"
-#elif SOURCE_ENGINE == SE_ORANGEBOX
+#elif (SOURCE_ENGINE == SE_ORANGEBOX) || (SOURCE_ENGINE == SE_ORANGEBOXVALVE)
 #include "convar_sm_ob.h"
 #else
 #include "convar_sm.h"