diff --git a/src/maths/ni/nidest.c b/src/maths/ni/nidest.c
index 0982e60f1..240b58fdf 100644
--- a/src/maths/ni/nidest.c
+++ b/src/maths/ni/nidest.c
@@ -18,7 +18,7 @@ NIdestroy(CKTcircuit *ckt)
 {
     if (ckt->CKTmatrix)
 	SMPdestroy(ckt->CKTmatrix);
-    ckt->CKTmatrix = NULL;
+    FREE(ckt->CKTmatrix);
     if(ckt->CKTrhs)         FREE(ckt->CKTrhs);
     if(ckt->CKTrhsOld)      FREE(ckt->CKTrhsOld);
     if(ckt->CKTrhsSpare)    FREE(ckt->CKTrhsSpare);
diff --git a/src/spicelib/analysis/cktdest.c b/src/spicelib/analysis/cktdest.c
index eb95283e2..24ed208d8 100644
--- a/src/spicelib/analysis/cktdest.c
+++ b/src/spicelib/analysis/cktdest.c
@@ -68,7 +68,7 @@ CKTdestroy(CKTcircuit *ckt)
     }
     if(ckt->CKTmatrix) {
         SMPdestroy(ckt->CKTmatrix);
-        ckt->CKTmatrix = NULL;
+        FREE(ckt->CKTmatrix);
     }
     FREE(ckt->CKTbreaks);
     for(node = ckt->CKTnodes; node; ) {