diff --git a/iseq.c b/iseq.c
index 07d8828e9b..9d1fdcc637 100644
--- a/iseq.c
+++ b/iseq.c
@@ -793,9 +793,14 @@ iseqw_s_compile(int argc, VALUE *argv, VALUE self)
       case 3: path = argv[--i];
       case 2: file = argv[--i];
     }
+
     if (NIL_P(file)) file = rb_fstring_cstr("<compiled>");
+    if (NIL_P(path)) path = file;
     if (NIL_P(line)) line = INT2FIX(1);
 
+    Check_Type(path, T_STRING);
+    Check_Type(file, T_STRING);
+
     return iseqw_new(rb_iseq_compile_with_option(src, file, path, line, 0, opt));
 }
 
diff --git a/version.h b/version.h
index 0c53981b31..b671f54de3 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.4.5"
 #define RUBY_RELEASE_DATE "2018-10-17"
-#define RUBY_PATCHLEVEL 325
+#define RUBY_PATCHLEVEL 326
 
 #define RUBY_RELEASE_YEAR 2018
 #define RUBY_RELEASE_MONTH 10