diff --git a/include/string.h b/include/string.h
index 43ad0942..35df7527 100644
--- a/include/string.h
+++ b/include/string.h
@@ -88,7 +88,7 @@ void explicit_bzero (void *, size_t);
 #endif
 
 #ifdef _GNU_SOURCE
-#define	strdupa(x)	strcpy(alloca(strlen(x)+1),x)
+#define	strdupa(x)	strcpy((char*)alloca(strlen(x)+1),x)
 int strverscmp (const char *, const char *);
 char *strchrnul(const char *, int);
 char *strcasestr(const char *, const char *);
