diff --git a/test/run b/test/run
index dd243120e82..8013efe4aba 100755
--- a/test/run
+++ b/test/run
@@ -23,6 +23,10 @@ RUNFILE=/tmp/gorun-$USER
 TMP1FILE=/tmp/gotest1-$USER
 TMP2FILE=/tmp/gotest2-$USER
 
+# don't run the machine out of memory: limit individual processes to 4GB.
+# on thresher, 3GB suffices to run the tests; with 2GB, peano fails.
+ulimit -v 4000000
+
 for dir in . ken chan bugs fixedbugs
 do
 	for i in $dir/*.go