diff --git a/copying_router_test.go b/copying_router_test.go
index 22c6834..7c02c45 100644
--- a/copying_router_test.go
+++ b/copying_router_test.go
@@ -30,7 +30,7 @@ func TestNewCopyingRouter(t *testing.T) {
 	}
 
 
-	message := fmt.Sprint("%x", randomness.Int63n(9999999999))
+	message := fmt.Sprintf("%x", randomness.Int63n(9999999999))
 
 	context := make(map[string]interface{})
 	limit := randomness.Int63n(30)
diff --git a/discarding_router_test.go b/discarding_router_test.go
index 45e5304..3e356e6 100644
--- a/discarding_router_test.go
+++ b/discarding_router_test.go
@@ -21,7 +21,7 @@ func TestNewDiscardingRouter(t *testing.T) {
 	}
 
 
-	message := fmt.Sprint("%x", randomness.Int63n(9999999999))
+	message := fmt.Sprintf("%x", randomness.Int63n(9999999999))
 
 	context := make(map[string]interface{})
 	limit := randomness.Int63n(30)
diff --git a/fanout_router_test.go b/fanout_router_test.go
index 432ddfc..83f5993 100644
--- a/fanout_router_test.go
+++ b/fanout_router_test.go
@@ -23,7 +23,7 @@ func TestNewFanoutRouter(t *testing.T) {
 	}
 
 
-	message := fmt.Sprint("%x", randomness.Int63n(9999999999))
+	message := fmt.Sprintf("%x", randomness.Int63n(9999999999))
 
 	context := make(map[string]interface{})
 	limit := randomness.Int63n(30)
diff --git a/filtering_router_test.go b/filtering_router_test.go
index adb5f4d..e5ff34d 100644
--- a/filtering_router_test.go
+++ b/filtering_router_test.go
@@ -23,7 +23,7 @@ func TestFilteringRouterJustCreated(t *testing.T) {
 	}
 
 
-	message := fmt.Sprint("%x", randomness.Int63n(9999999999))
+	message := fmt.Sprintf("%x", randomness.Int63n(9999999999))
 
 	context := make(map[string]interface{})
 	limit := randomness.Int63n(30)