diff --git a/src/spicelib/parser/inpptree.c b/src/spicelib/parser/inpptree.c
index 0dac42703..956b190cc 100644
--- a/src/spicelib/parser/inpptree.c
+++ b/src/spicelib/parser/inpptree.c
@@ -1409,6 +1409,9 @@ void INPfreeTree(IFparseTree *ptree)
 
     int i;
 
+    if (!pt)
+        return;
+
     for (i = 0; i < pt->p.numVars; i++)
         dec_usage(pt->derivs[i]);