diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 4fd0084a..0b3f025f 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -167,7 +167,11 @@ endif()
 
 if (GLFW_BUILD_OS4)
     target_compile_options(glfw PRIVATE "-DGL4ES" "-gstabs")
-    target_link_libraries(glfw PRIVATE "-lGL")
+    if (CLIB4)
+        target_link_libraries(glfw PRIVATE "-lGL")
+    else()
+        target_link_libraries(glfw PRIVATE "-lgl4es -ldl")
+    endif()
 endif()
 
 if (GLFW_BUILD_COCOA)
diff --git a/src/os4_init.c b/src/os4_init.c
index 6b5d7384..ef8d8f9b 100644
--- a/src/os4_init.c
+++ b/src/os4_init.c
@@ -29,9 +29,15 @@
 
 #include "internal.h"
 
+#ifndef CLIB4
+#undef __STRICT_ANSI__
+#endif
+
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
+#include <stdarg.h>
+#include <unistd.h>
 
 extern struct Library *DOSBase;
 extern struct DOSIFace *IDOS;