diff --git a/cinelerra-5.1/libzmpeg3/libzmpeg3.h b/cinelerra-5.1/libzmpeg3/libzmpeg3.h
index 430ebb4..9bd02e6 100644
--- a/cinelerra-5.1/libzmpeg3/libzmpeg3.h
+++ b/cinelerra-5.1/libzmpeg3/libzmpeg3.h
@@ -5,7 +5,9 @@
 /* for quicktime build */
 #define MAXFRAMESAMPLES 65536
 #define ZDVB
+#if __x86_64__ || __i386__
 #define USE_FUTEX
+#endif
 
 #ifndef __STDC_LIMIT_MACROS
 #define __STDC_LIMIT_MACROS