diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
index fa1a5e67d6..ad7bd09ceb 100644
--- a/src/cmd/dist/test.go
+++ b/src/cmd/dist/test.go
@@ -451,6 +451,11 @@ func (t *tester) registerTests() {
 		t.registerTest("wiki", "../doc/articles/wiki", "./test.bash")
 		t.registerTest("codewalk", "../doc/codewalk", "time", "./run")
 		for _, name := range t.shootoutTests() {
+			if name == "spectralnorm" && os.Getenv("GO_BUILDER_NAME") == "linux-arm-arm5" {
+				// Heavy on floating point and takes over 20 minutes with softfloat.
+				// Disabled per Issue 12688.
+				continue
+			}
 			t.registerTest("shootout:"+name, "../test/bench/shootout", "time", "./timing.sh", "-test", name)
 		}
 	}