diff --git a/src/racket/sconfig.h b/src/racket/sconfig.h
index b0fad01e55..612a5c0c9a 100644
--- a/src/racket/sconfig.h
+++ b/src/racket/sconfig.h
@@ -88,6 +88,8 @@
 /* Solaris */
 #  if  defined(i386)
 #   define SCHEME_PLATFORM_LIBRARY_SUBPATH "i386-solaris"
+#  elif defined(__x86_64)
+#   define SCHEME_PLATFORM_LIBRARY_SUBPATH "x86_64-solaris"
 #  else
 #   define SCHEME_PLATFORM_LIBRARY_SUBPATH "sparc-solaris"
 #  endif
@@ -108,17 +110,18 @@
 # define USE_ON_EXIT_FOR_ATEXIT
 # endif
 
-#define FMOD_CAN_RETURN_POS_ZERO
+# define FMOD_CAN_RETURN_POS_ZERO
 
-# ifndef i386
+# ifdef i386
+#  define MZ_USE_JIT_I386
+#  define MZ_JIT_USE_MPROTECT
+# elif defined(__x86_64)
+#  define MZ_USE_JIT_X86_64
+#  define MZ_JIT_USE_MPROTECT
+# else
 #  define FLUSH_SPARC_REGISTER_WINDOWS
 # endif
 
-#ifdef i386
-# define MZ_USE_JIT_I386
-# define MZ_JIT_USE_MPROTECT
-#endif
-
 # define FLAGS_ALREADY_SET
 
 #endif