diff --git a/rdrand.cpp b/rdrand.cpp
index 55fde3ab..5d7b8e2e 100644
--- a/rdrand.cpp
+++ b/rdrand.cpp
@@ -253,7 +253,11 @@ static int GCC_RRA_GenerateBlock(byte *output, size_t size, unsigned int safety)
 			"setc %1; "
 			: "=a" (val), "=qm" (rc)
 			:
-			: "cc"
+#if CRYPTOPP_BOOL_X64 || CRYPTOPP_BOOL_X32
+			: "rax", "cc"
+#else
+			: "eax", "cc"
+#endif
         );
 
 		if (rc)
@@ -434,7 +438,11 @@ static int GCC_RSA_GenerateBlock(byte *output, size_t size, unsigned int safety)
 			"setc %1; "
 			: "=a" (val), "=qm" (rc)
 			:
-			: "cc"
+#if CRYPTOPP_BOOL_X64 || CRYPTOPP_BOOL_X32
+			: "rax", "cc"
+#else
+			: "eax", "cc"
+#endif
         );
 
 		if (rc)