diff --git a/cffi_build.py.in b/cffi_build.py.in
index 7d2b8678284d5335411b08d68daf2a46677ab388..3e4d6086d424127f505f71091cac973e00aa0cc0 100644
--- a/cffi_build.py.in
+++ b/cffi_build.py.in
@@ -43,7 +43,7 @@ with open("src/c_wrapper/wrap_cl_core.h", "rt") as f:
     ffi.cdef(f.read())
 
 if {CL_ENABLE_GL}:
-    with open("wrap_cl_gl_core.h") as f:
+    with open("src/c_wrapper/wrap_cl_gl_core.h") as f:
         ffi.cdef(f.read())
 
 ffi.set_source("pyopencl._cffi",