diff --git a/libqpdf/Pl_Flate.cc b/libqpdf/Pl_Flate.cc
index be8ca8ba..297cdac7 100644
--- a/libqpdf/Pl_Flate.cc
+++ b/libqpdf/Pl_Flate.cc
@@ -77,8 +77,10 @@ Pl_Flate::handleData(unsigned char* data, int len, int flush)
         // deflateInit and inflateInit are macros that use old-style
         // casts.
 #ifdef __GNUC__
+# if ((__GNUC__ * 100) + __GNUC_MINOR__) >= 406
 #       pragma GCC diagnostic push
 #       pragma GCC diagnostic ignored "-Wold-style-cast"
+# endif
 #endif
 	if (this->action == a_deflate)
 	{
@@ -89,7 +91,9 @@ Pl_Flate::handleData(unsigned char* data, int len, int flush)
 	    err = inflateInit(&zstream);
 	}
 #ifdef __GNUC__
+# if ((__GNUC__ * 100) + __GNUC_MINOR__) >= 406
 #       pragma GCC diagnostic pop
+# endif
 #endif
 
 	checkError("Init", err);