diff --git a/config/config.go b/config/config.go
index 220032585..bb3f5f1c8 100644
--- a/config/config.go
+++ b/config/config.go
@@ -807,7 +807,7 @@ func (v *Variable) ValidateTypeAndDefault() error {
 	// If an explicit type is declared, ensure it is valid
 	if v.DeclaredType != "" {
 		if _, ok := typeStringMap[v.DeclaredType]; !ok {
-			return fmt.Errorf("Variable '%s' must be of type string or map", v.Name)
+			return fmt.Errorf("Variable '%s' must be of type string or map - '%s' is not a valid type", v.Name, v.DeclaredType)
 		}
 	}