diff --git a/cl_dll/CMakeLists.txt b/cl_dll/CMakeLists.txt
index 1143eefe..3e5b7dbf 100644
--- a/cl_dll/CMakeLists.txt
+++ b/cl_dll/CMakeLists.txt
@@ -25,6 +25,11 @@ project (CLDLL)
 
 set (CLDLL_LIBRARY client)
 
+include(CheckIncludeFile)
+check_include_file("tgmath.h" HAVE_TGMATH_H)
+if(HAVE_TGMATH_H)
+	add_definitions(-DHAVE_TGMATH_H)
+endif()
 
 add_definitions(-DCLIENT_WEAPONS -DCLIENT_DLL)
 
diff --git a/dlls/CMakeLists.txt b/dlls/CMakeLists.txt
index ccaa0279..9baf9479 100644
--- a/dlls/CMakeLists.txt
+++ b/dlls/CMakeLists.txt
@@ -25,6 +25,12 @@ project (SVDLL)
 
 set (SVDLL_LIBRARY server)
 
+include(CheckIncludeFile)
+check_include_file("tgmath.h" HAVE_TGMATH_H)
+if(HAVE_TGMATH_H)
+	add_definitions(-DHAVE_TGMATH_H)
+endif()
+
 add_definitions(-DCLIENT_WEAPONS)
 
 if(NOT MSVC)