diff --git a/src/cmd/api/goapi.go b/src/cmd/api/goapi.go
index 036aefe4d8..5ae059e4ce 100644
--- a/src/cmd/api/goapi.go
+++ b/src/cmd/api/goapi.go
@@ -459,8 +459,11 @@ type listImports struct {
 
 var listCache sync.Map // map[string]listImports, keyed by contextName
 
-// listSem is a semaphore restricting concurrent invocations of 'go list'.
-var listSem = make(chan semToken, ((runtime.GOMAXPROCS(0)-1)/2)+1)
+// listSem is a semaphore restricting concurrent invocations of 'go list'. 'go
+// list' has its own internal concurrency, so we use a hard-coded constant (to
+// allow the I/O-intensive phases of 'go list' to overlap) instead of scaling
+// all the way up to GOMAXPROCS.
+var listSem = make(chan semToken, 2)
 
 type semToken struct{}