diff --git a/ext2spice/ext2hier.c b/ext2spice/ext2hier.c
index 4e381ea5..0e352990 100644
--- a/ext2spice/ext2hier.c
+++ b/ext2spice/ext2hier.c
@@ -1499,10 +1499,10 @@ spcnodeHierVisit(
  */
 static char esTempName[MAX_STR_SIZE];
 
-char *
+const char *
 nodeSpiceHierName(
     HierContext *hc,
-    HierName *hname)
+    const HierName *hname)
 {
     EFNodeName *nn;
     HashEntry *he, *he2;
diff --git a/ext2spice/ext2spice.h b/ext2spice/ext2spice.h
index fd5fb677..c41c86f3 100644
--- a/ext2spice/ext2spice.h
+++ b/ext2spice/ext2spice.h
@@ -36,7 +36,7 @@ extern int nodeVisitDebug(EFNode *node, int res, double cap, ClientData cdata);
 extern void topVisit(Def *def, bool doStub);
 extern void swapDrainSource(Dev *dev);
 
-extern char *nodeSpiceHierName(HierContext *hc, HierName *hname);
+extern const char *nodeSpiceHierName(HierContext *hc, const HierName *hname);
 extern devMerge *mkDevMerge(float l, float w, EFNode *g, EFNode *s, EFNode *d, EFNode *b, HierName *hn, Dev *dev);
 extern bool extHierSDAttr(DevTerm *term);