diff --git a/make/RunTests.gmk b/make/RunTests.gmk
index 546a85f1659..fbd5c35bb22 100644
--- a/make/RunTests.gmk
+++ b/make/RunTests.gmk
@@ -738,7 +738,7 @@ define SetupRunJtregTestBody
 
   # Make sure MaxRAMPercentage is high enough to not cause OOM or swapping since
   # we may end up with a lot of JVM's
-  $1_JTREG_MAX_RAM_PERCENTAGE := $$(shell $$(EXPR) 25 / $$($1_JTREG_JOBS))
+  $1_JTREG_MAX_RAM_PERCENTAGE := $$(shell $(AWK) 'BEGIN { print 25 / $$($1_JTREG_JOBS); }')
 
   JTREG_TIMEOUT_FACTOR ?= 4