diff --git a/CMakeLists.txt b/CMakeLists.txt
old mode 100644
new mode 100755
index 82a1ad32..11db057e
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,10 +12,16 @@ else()
   set (CMAKE_C_STANDARD 99)
 endif()
 include(CheckCCompilerFlag)
-CHECK_C_COMPILER_FLAG("-Werror=pointer-arith" COMPILER_HAS_POINTER_ARITH_TOGGLE)
-if(COMPILER_HAS_POINTER_ARITH_TOGGLE)
-    set(CMAKE_C_FLAGS "-Werror=pointer-arith ${CMAKE_C_FLAGS}")
-endif()
+foreach(option -Werror=pointer-arith;-Werror=implicit-function-declaration)
+    CHECK_C_COMPILER_FLAG("${option}" COMPILER_HAS_THOSE_TOGGLES)
+    set(outcome "Failed")
+    if(COMPILER_HAS_THOSE_TOGGLES)
+        set(CMAKE_C_FLAGS "${option} ${CMAKE_C_FLAGS}")
+        set(outcome "works")
+    endif()
+    message(STATUS "Testing if ${option} can be used -- ${outcome}")
+endforeach()
+
 
 add_subdirectory(src release)
 
diff --git a/src/Makefile b/src/Makefile
index c88aa6dd..fc85ea0a 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -262,7 +262,8 @@ endif
 #  -Wno-missing-braces   ignore invalid warning (GCC bug 53119)
 #  -D_DEFAULT_SOURCE     use with -std=c99 on Linux and PLATFORM_WEB, required for timespec
 #  -Werror=pointer-arith catch unportable code that does direct arithmetic on void pointers
-CFLAGS += -O1 -Wall -std=c99 -D_DEFAULT_SOURCE -fgnu89-inline -Wno-missing-braces -Werror=pointer-arith
+#  -Werror=implicit-function-declaration catch function calls without prior declaration
+CFLAGS += -O1 -Wall -std=c99 -D_DEFAULT_SOURCE -fgnu89-inline -Wno-missing-braces -Werror=pointer-arith -Werror=implicit-function-declaration
 
 ifeq ($(RAYLIB_BUILD_MODE), DEBUG)
     CFLAGS += -g
diff --git a/src/physac.h b/src/physac.h
index a04d3cb3..463d8950 100644
--- a/src/physac.h
+++ b/src/physac.h
@@ -255,6 +255,7 @@ PHYSACDEF void ClosePhysics(void);
     // Functions required to query time on Windows
     int __stdcall QueryPerformanceCounter(unsigned long long int *lpPerformanceCount);
     int __stdcall QueryPerformanceFrequency(unsigned long long int *lpFrequency);
+    #include <time.h>
 #elif defined(__linux__)
     #if _POSIX_C_SOURCE < 199309L
         #undef _POSIX_C_SOURCE
diff --git a/src/rlgl.c b/src/rlgl.c
index d325a1bd..63860f1c 100644
--- a/src/rlgl.c
+++ b/src/rlgl.c
@@ -74,6 +74,7 @@
 #if defined(GRAPHICS_API_OPENGL_11)
     #if defined(__APPLE__)
         #include <OpenGL/gl.h>      // OpenGL 1.1 library for OSX
+        #include <OpenGL/glext.h>
     #else
 		#if defined(_MSC_VER)		// Using MSVC compiler, requires some additional definitions
 			// APIENTRY for OpenGL function pointer declarations is required
@@ -101,6 +102,7 @@
 #if defined(GRAPHICS_API_OPENGL_33)
     #if defined(__APPLE__)
         #include <OpenGL/gl3.h>     // OpenGL 3 library for OSX
+        #include <OpenGL/gl3ext.h>
     #else
         #define GLAD_IMPLEMENTATION
         #if defined(RLGL_STANDALONE)
@@ -125,6 +127,7 @@
     #include "shader_distortion.h"  // Distortion shader to be embedded
 #endif
 
+
 //----------------------------------------------------------------------------------
 // Defines and Macros
 //----------------------------------------------------------------------------------