diff --git a/lsteamclient/cppISteamClient_SteamClient016.cpp b/lsteamclient/cppISteamClient_SteamClient016.cpp
index 7b1c7d5c..e84c3383 100644
--- a/lsteamclient/cppISteamClient_SteamClient016.cpp
+++ b/lsteamclient/cppISteamClient_SteamClient016.cpp
@@ -174,6 +174,7 @@ void cppISteamClient_SteamClient016_Remove_SteamAPI_CPostAPIResultInProcess(void
 
 void cppISteamClient_SteamClient016_Set_SteamAPI_CCheckCallbackRegisteredInProcess(void *linux_side, SteamAPI_CheckCallbackRegistered_t func)
 {
+    func = (SteamAPI_CheckCallbackRegistered_t)manual_convert_SteamAPI_CheckCallbackRegistered_t((void*)func);
     ((ISteamClient*)linux_side)->Set_SteamAPI_CCheckCallbackRegisteredInProcess((SteamAPI_CheckCallbackRegistered_t)func);
 }
 
diff --git a/lsteamclient/cppISteamClient_SteamClient017.cpp b/lsteamclient/cppISteamClient_SteamClient017.cpp
index 0a7e1927..7a6d65d1 100644
--- a/lsteamclient/cppISteamClient_SteamClient017.cpp
+++ b/lsteamclient/cppISteamClient_SteamClient017.cpp
@@ -174,6 +174,7 @@ void cppISteamClient_SteamClient017_DEPRECATED_Remove_SteamAPI_CPostAPIResultInP
 
 void cppISteamClient_SteamClient017_Set_SteamAPI_CCheckCallbackRegisteredInProcess(void *linux_side, SteamAPI_CheckCallbackRegistered_t func)
 {
+    func = (SteamAPI_CheckCallbackRegistered_t)manual_convert_SteamAPI_CheckCallbackRegistered_t((void*)func);
     ((ISteamClient*)linux_side)->Set_SteamAPI_CCheckCallbackRegisteredInProcess((SteamAPI_CheckCallbackRegistered_t)func);
 }
 
diff --git a/lsteamclient/cppISteamClient_SteamClient018.cpp b/lsteamclient/cppISteamClient_SteamClient018.cpp
index d59370b4..1050990d 100644
--- a/lsteamclient/cppISteamClient_SteamClient018.cpp
+++ b/lsteamclient/cppISteamClient_SteamClient018.cpp
@@ -180,6 +180,7 @@ void cppISteamClient_SteamClient018_DEPRECATED_Remove_SteamAPI_CPostAPIResultInP
 
 void cppISteamClient_SteamClient018_Set_SteamAPI_CCheckCallbackRegisteredInProcess(void *linux_side, SteamAPI_CheckCallbackRegistered_t func)
 {
+    func = (SteamAPI_CheckCallbackRegistered_t)manual_convert_SteamAPI_CheckCallbackRegistered_t((void*)func);
     ((ISteamClient*)linux_side)->Set_SteamAPI_CCheckCallbackRegisteredInProcess((SteamAPI_CheckCallbackRegistered_t)func);
 }
 
diff --git a/lsteamclient/gen_wrapper.py b/lsteamclient/gen_wrapper.py
index aa145e59..bb12bfe8 100755
--- a/lsteamclient/gen_wrapper.py
+++ b/lsteamclient/gen_wrapper.py
@@ -5,7 +5,7 @@
 
 from __future__ import print_function
 
-CLANG_PATH='/usr/lib/clang/8.0.0'
+CLANG_PATH='/usr/lib/clang/8.0.1'
 
 import pprint
 import sys
@@ -178,7 +178,8 @@ manually_handled_methods = {
 
 # manual converters for simple types (function pointers)
 manual_type_converters = [
-        "FSteamNetworkingSocketsDebugOutput"
+        "FSteamNetworkingSocketsDebugOutput",
+        "SteamAPI_CheckCallbackRegistered_t"
 ]
 
 # manual converters for specific parameters
diff --git a/lsteamclient/steam_defs.h b/lsteamclient/steam_defs.h
index 058085b2..22586555 100644
--- a/lsteamclient/steam_defs.h
+++ b/lsteamclient/steam_defs.h
@@ -205,11 +205,9 @@ typedef struct SteamNetworkingQuickConnectionStatus SteamNetworkingQuickConnecti
 typedef struct SteamDatagramRelayAuthTicket SteamDatagramRelayAuthTicket;
 typedef struct SteamDatagramHostedAddress SteamDatagramHostedAddress;
 
-/* FIXME: we don't care about fn pointer types, just pass 'em through */
-typedef void *SteamAPI_CheckCallbackRegistered_t;
-typedef void *SteamAPIWarningMessageHook_t;
-typedef void *SteamAPI_PostAPIResultInProcess_t;
-
+typedef uint32 (*SteamAPI_CheckCallbackRegistered_t)(int cb);
+typedef void *SteamAPIWarningMessageHook_t; //already cdecl, no need for conversion(?)
+typedef void *SteamAPI_PostAPIResultInProcess_t; //unused
 typedef void (*FSteamNetworkingSocketsDebugOutput)(ESteamNetworkingSocketsDebugOutputType nType, const char *pszMsg);
 
 typedef uint8 Salt_t[8];
diff --git a/lsteamclient/steamclient_private.h b/lsteamclient/steamclient_private.h
index 64f32945..8b600ee6 100644
--- a/lsteamclient/steamclient_private.h
+++ b/lsteamclient/steamclient_private.h
@@ -48,6 +48,7 @@ void *create_LinuxISteamMatchmakingPingResponse(void *win, const char *version);
 void *create_LinuxISteamMatchmakingPlayersResponse(void *win, const char *version);
 void *create_LinuxISteamMatchmakingRulesResponse(void *win, const char *version);
 void *manual_convert_FSteamNetworkingSocketsDebugOutput(void *win_func);
+void *manual_convert_SteamAPI_CheckCallbackRegistered_t(void *win_func);
 
 extern char g_tmppath[PATH_MAX];
 
diff --git a/lsteamclient/steamclient_wrappers.c b/lsteamclient/steamclient_wrappers.c
index aa62067e..a7f2b1c6 100644
--- a/lsteamclient/steamclient_wrappers.c
+++ b/lsteamclient/steamclient_wrappers.c
@@ -295,3 +295,18 @@ void *manual_convert_FSteamNetworkingSocketsDebugOutput(void *win_func)
     stored_FSteamNetworkingSocketsDebugOutput = (void*)win_func;
     return &lin_FSteamNetworkingSocketsDebugOutput;
 }
+
+
+/***** SteamAPI_CheckCallbackRegistered_t *****/
+static uint32 (__attribute__((ms_abi)) *stored_SteamAPI_CheckCallbackRegistered_t)(int cb);
+
+static uint32 lin_SteamAPI_CheckCallbackRegistered_t(int cb)
+{
+    return stored_SteamAPI_CheckCallbackRegistered_t(cb);
+}
+
+void *manual_convert_SteamAPI_CheckCallbackRegistered_t(void *win_func)
+{
+    stored_SteamAPI_CheckCallbackRegistered_t = (void*)win_func;
+    return &lin_SteamAPI_CheckCallbackRegistered_t;
+}