diff --git a/galois_amd64.go b/galois_amd64.go
index <HASH>..<HASH> 100644
--- a/galois_amd64.go
+++ b/galois_amd64.go
@@ -1,4 +1,5 @@
 //+build !noasm
+//+build !appengine
 
 // Copyright 2015, Klaus Post, see LICENSE for details.
 
diff --git a/galois_amd64.s b/galois_amd64.s
index <HASH>..<HASH> 100644
--- a/galois_amd64.s
+++ b/galois_amd64.s
@@ -1,4 +1,4 @@
-//+build !noasm
+//+build !noasm !appengine
 
 // Copyright 2015, Klaus Post, see LICENSE for details.
 
diff --git a/galois_noasm.go b/galois_noasm.go
index <HASH>..<HASH> 100644
--- a/galois_noasm.go
+++ b/galois_noasm.go
@@ -1,4 +1,4 @@
-//+build !amd64 noasm
+//+build !amd64 noasm appengine
 
 // Copyright 2015, Klaus Post, see LICENSE for details.
Don't use assembler on app engine.