diff --git a/overrides_test.go b/overrides_test.go
index dd2aa9b..ed59e70 100644
--- a/overrides_test.go
+++ b/overrides_test.go
@@ -155,11 +155,11 @@ func deepCheckValue(assert *assert.Assertions, v *Viper, l layer, keys []string,
 		}
 
 		// deep scan of the map to get the final value
-		switch val.(type) {
+		switch v := val.(type) {
 		case map[interface{}]interface{}:
 			m = cast.ToStringMap(val)
 		case map[string]interface{}:
-			m = val.(map[string]interface{})
+			m = v
 		default:
 			assert.Fail(fmt.Sprintf("%s is not a map[string]interface{}", ms))
 			return
diff --git a/util.go b/util.go
index 952cad4..178f112 100644
--- a/util.go
+++ b/util.go
@@ -68,14 +68,14 @@ func copyAndInsensitiviseMap(m map[string]interface{}) map[string]interface{} {
 
 func insensitiviseMap(m map[string]interface{}) {
 	for key, val := range m {
-		switch val.(type) {
+		switch v := val.(type) {
 		case map[interface{}]interface{}:
 			// nested map: cast and recursively insensitivise
 			val = cast.ToStringMap(val)
 			insensitiviseMap(val.(map[string]interface{}))
 		case map[string]interface{}:
 			// nested map: recursively insensitivise
-			insensitiviseMap(val.(map[string]interface{}))
+			insensitiviseMap(v)
 		}
 
 		lower := strings.ToLower(key)
diff --git a/viper.go b/viper.go
index a32ab73..b82a788 100644
--- a/viper.go
+++ b/viper.go
@@ -491,13 +491,13 @@ func (v *Viper) searchMap(source map[string]interface{}, path []string) interfac
 		}
 
 		// Nested case
-		switch next.(type) {
+		switch n := next.(type) {
 		case map[interface{}]interface{}:
 			return v.searchMap(cast.ToStringMap(next), path[1:])
 		case map[string]interface{}:
 			// Type assertion is safe here since it is only reached
 			// if the type of `next` is the same as the type being asserted
-			return v.searchMap(next.(map[string]interface{}), path[1:])
+			return v.searchMap(n, path[1:])
 		default:
 			// got a value but nested key expected, return "nil" for not found
 			return nil
@@ -535,13 +535,13 @@ func (v *Viper) searchMapWithPathPrefixes(source map[string]interface{}, path []
 
 			// Nested case
 			var val interface{}
-			switch next.(type) {
+			switch n := next.(type) {
 			case map[interface{}]interface{}:
 				val = v.searchMapWithPathPrefixes(cast.ToStringMap(next), path[i:])
 			case map[string]interface{}:
 				// Type assertion is safe here since it is only reached
 				// if the type of `next` is the same as the type being asserted
-				val = v.searchMapWithPathPrefixes(next.(map[string]interface{}), path[i:])
+				val = v.searchMapWithPathPrefixes(n, path[i:])
 			default:
 				// got a value but nested key expected, do nothing and look for next prefix
 			}
@@ -1675,9 +1675,9 @@ func (v *Viper) flattenAndMergeMap(shadow map[string]bool, m map[string]interfac
 	}
 	for k, val := range m {
 		fullKey := prefix + k
-		switch val.(type) {
+		switch v := val.(type) {
 		case map[string]interface{}:
-			m2 = val.(map[string]interface{})
+			m2 = v
 		case map[interface{}]interface{}:
 			m2 = cast.ToStringMap(val)
 		default: