--- a/IlmBase.pc.in
+++ b/IlmBase.pc.in
@@ -15,3 +15,4 @@ Requires:
 Conflicts:
 Libs: -L${libdir} -lImath${libsuffix} -lHalf${libsuffix} -lIex${libsuffix} -lIexMath${libsuffix} -lIlmThread${libsuffix} @PTHREAD_LIBS@
 Cflags: @PTHREAD_CFLAGS@ -I${includedir} -I${includedir}/OpenEXR
+Requires.private: gl glu