diff --git a/src/Crypto/jitterentropy-base-user.h b/src/Crypto/jitterentropy-base-user.h
index b32d8ed3..aaefb41a 100644
--- a/src/Crypto/jitterentropy-base-user.h
+++ b/src/Crypto/jitterentropy-base-user.h
@@ -85,6 +85,8 @@ static VC_INLINE void jent_get_nstime(uint64 *out)
 
 #else
 
+#include <sys/types.h>
+
 #if CRYPTOPP_BOOL_X86 || CRYPTOPP_BOOL_X32 || CRYPTOPP_BOOL_X64
 
 /* taken from Linux kernel */