diff --git a/cmd/dep/root_analyzer.go b/cmd/dep/root_analyzer.go
index b7d278fe25..9e775887f6 100644
--- a/cmd/dep/root_analyzer.go
+++ b/cmd/dep/root_analyzer.go
@@ -60,6 +60,8 @@ func (a *rootAnalyzer) cacheDeps(pr gps.ProjectRoot) {
 	packages := make(map[string]bool)
 	dependencies := make(map[gps.ProjectRoot][]string)
 	logger := a.ctx.Err
+	concurrency := 4
+	sem := make(chan bool, concurrency)
 
 	syncDep := func(pr gps.ProjectRoot, sm gps.SourceManager) {
 		if err := sm.SyncSourceFor(gps.ProjectIdentifier{ProjectRoot: pr}); err != nil {
@@ -90,9 +92,16 @@ func (a *rootAnalyzer) cacheDeps(pr gps.ProjectRoot) {
 			continue
 		}
 
-		go syncDep(pr, a.sm)
+		sem <- true
+		go func() {
+			defer func() { <-sem }()
+			go syncDep(pr, a.sm)
+		}()
 		dependencies[pr] = []string{ip}
 	}
+	for i := 0; i < cap(sem); i++ {
+		sem <- true
+	}
 }
 
 func hasImportPathPrefix(s, prefix string) bool {