diff --git a/core/c/mpw-types.c b/core/c/mpw-types.c
index ad74b057..fd144bbb 100644
--- a/core/c/mpw-types.c
+++ b/core/c/mpw-types.c
@@ -22,6 +22,9 @@
 #include "mpw-types.h"
 #include "mpw-util.h"
 
+const size_t MPMasterKeySize = 64;
+const size_t MPSiteKeySize = 256 / 8; // Size of HMAC-SHA-256
+
 const MPResultType mpw_typeWithName(const char *typeName) {
 
     // Find what password type is represented by the type letter.
diff --git a/core/c/mpw-types.h b/core/c/mpw-types.h
index fa56c819..95208040 100644
--- a/core/c/mpw-types.h
+++ b/core/c/mpw-types.h
@@ -35,10 +35,8 @@
 
 //// Types.
 
-#define MPMasterKeySize 64 /* bytes */
-typedef const uint8_t *MPMasterKey;
-#define MPSiteKeySize (256 / 8) /* bytes */ // Size of HMAC-SHA-256
-typedef const uint8_t *MPSiteKey;
+extern const size_t MPMasterKeySize, MPSiteKeySize; /* bytes */
+typedef const uint8_t *MPMasterKey, *MPSiteKey;
 typedef const char *MPKeyID;
 
 typedef mpw_enum( uint8_t, MPKeyPurpose ) {