diff --git a/container/container.go b/container/container.go
index 48ba72e..c49da33 100644
--- a/container/container.go
+++ b/container/container.go
@@ -136,7 +136,12 @@ func (c Container) runtimeConfig() *dockercontainer.Config {
 
 	config.Volumes = structMapSubtract(config.Volumes, imageConfig.Volumes)
 
-	config.ExposedPorts = structMapPortSubtract(config.ExposedPorts, imageConfig.ExposedPorts)
+	// subtract ports exposed in image from container
+	for k, _ := range config.ExposedPorts {
+		if _, ok := imageConfig.ExposedPorts[k]; ok {
+			delete(config.ExposedPorts, k)
+		}
+	}
 	for p := range c.containerInfo.HostConfig.PortBindings {
 		config.ExposedPorts[p] = struct{}{}
 	}
diff --git a/container/util.go b/container/util.go
index 184b491..8947c82 100644
--- a/container/util.go
+++ b/container/util.go
@@ -1,7 +1,6 @@
 package container
 
 import (
-	"github.com/docker/go-connections/nat"
 )
 
 func sliceEqual(s1, s2 []string) bool {
@@ -67,14 +66,3 @@ func structMapSubtract(m1, m2 map[string]struct{}) map[string]struct{} {
 	return m
 }
 
-func structMapPortSubtract(m1, m2 map[nat.Port]struct{}) map[nat.Port]struct{} {
-	m := map[nat.Port]struct{}{}
-
-	for k1, v1 := range m1 {
-		if _, ok := m2[k1]; !ok {
-			m[k1] = v1
-		}
-	}
-
-	return m
-}
diff --git a/container/util_test.go b/container/util_test.go
index c4d5ca7..9ed551d 100644
--- a/container/util_test.go
+++ b/container/util_test.go
@@ -63,3 +63,4 @@ func TestStructMapSubtract(t *testing.T) {
 	assert.Equal(t, map[string]struct{}{"a": x, "b": x, "c": x}, m1)
 	assert.Equal(t, map[string]struct{}{"a": x, "c": x}, m2)
 }
+