diff --git a/cc/sanitize.go b/cc/sanitize.go
index 0199897..0ed0d47 100644
--- a/cc/sanitize.go
+++ b/cc/sanitize.go
@@ -293,9 +293,13 @@
 	}
 
 	// cc_test targets default to SYNC MemTag unless explicitly set to ASYNC (via diag: {memtag_heap}).
-	if ctx.testBinary() && s.Memtag_heap == nil {
-		s.Memtag_heap = proptools.BoolPtr(true)
-		s.Diag.Memtag_heap = proptools.BoolPtr(true)
+	if ctx.testBinary() {
+		if s.Memtag_heap == nil {
+			s.Memtag_heap = proptools.BoolPtr(true)
+		}
+		if s.Diag.Memtag_heap == nil {
+			s.Diag.Memtag_heap = proptools.BoolPtr(true)
+		}
 	}
 
 	var globalSanitizers []string