diff --git a/algebra.cpp b/algebra.cpp
index 758939e6..78c3947b 100644
--- a/algebra.cpp
+++ b/algebra.cpp
@@ -2,8 +2,8 @@
 
 #include "pch.h"
 
-// prevent Sun's CC compiler from including this file automatically
-#if !defined(__SUNPRO_CC) || defined(CRYPTOPP_MANUALLY_INSTANTIATE_TEMPLATES)
+#ifndef CRYPTOPP_ALGEBRA_CPP	// SunCC workaround: compiler could cause this file to be included twice
+#define CRYPTOPP_ALGEBRA_CPP
 
 #include "algebra.h"
 #include "integer.h"
diff --git a/pkcspad.cpp b/pkcspad.cpp
index d90e4aba..7cee9b95 100644
--- a/pkcspad.cpp
+++ b/pkcspad.cpp
@@ -2,8 +2,8 @@
 
 #include "pch.h"
 
-// prevent Sun's CC compiler from including this file automatically
-#if !defined(__SUNPRO_CC) || defined(CRYPTOPP_MANUALLY_INSTANTIATE_TEMPLATES)
+#ifndef CRYPTOPP_PKCSPAD_CPP	// SunCC workaround: compiler could cause this file to be included twice
+#define CRYPTOPP_PKCSPAD_CPP
 
 #include "pkcspad.h"
 #include <assert.h>