diff --git a/eval_error.c b/eval_error.c
index fa9fa8cdab..e8a1691036 100644
--- a/eval_error.c
+++ b/eval_error.c
@@ -32,7 +32,7 @@ error_pos_str(void)
     int sourceline;
     VALUE sourcefile = rb_source_location(&sourceline);
 
-    if (sourcefile) {
+    if (!NIL_P(sourcefile)) {
 	ID caller_name;
 	if (sourceline == 0) {
 	    return rb_sprintf("%"PRIsVALUE": ", sourcefile);
diff --git a/vm.c b/vm.c
index 9ee90a52fd..e5f2c2fd99 100644
--- a/vm.c
+++ b/vm.c
@@ -1293,7 +1293,7 @@ rb_source_location(int *pline)
     }
     else {
 	if (pline) *pline = 0;
-	return 0;
+	return Qnil;
     }
 }
 
@@ -1301,7 +1301,7 @@ const char *
 rb_source_loc(int *pline)
 {
     VALUE path = rb_source_location(pline);
-    if (!path) return 0;
+    if (!NIL_P(path)) return NULL;
     return RSTRING_PTR(path);
 }