diff --git a/core/c/mpw-algorithm_v0.c b/core/c/mpw-algorithm_v0.c
index b98b474f..5dc7708b 100644
--- a/core/c/mpw-algorithm_v0.c
+++ b/core/c/mpw-algorithm_v0.c
@@ -126,7 +126,7 @@ static MPSiteKey mpw_siteKey_v0(
 }
 
 static const char *mpw_sitePasswordFromTemplate_v0(
-        MPMasterKey  __unused masterKey, MPSiteKey siteKey, MPResultType resultType, const char __unused *resultParam) {
+        MPMasterKey __unused masterKey, MPSiteKey siteKey, MPResultType resultType, const char __unused *resultParam) {
 
     const char *_siteKey = (const char *)siteKey;
 
diff --git a/core/c/mpw-types.h b/core/c/mpw-types.h
index 0318b3a7..990e6fef 100644
--- a/core/c/mpw-types.h
+++ b/core/c/mpw-types.h
@@ -29,6 +29,10 @@
 #define mpw_enum(_type, _name) _type _name; enum
 #endif
 
+#ifndef __unused
+#define __unused __attribute__((unused))
+#endif
+
 //// Types.
 
 #define MPMasterKeySize 64 /* bytes */