diff --git a/src/include/ngspice/inpptree.h b/src/include/ngspice/inpptree.h
index 68aa08c08..8dbfa032d 100644
--- a/src/include/ngspice/inpptree.h
+++ b/src/include/ngspice/inpptree.h
@@ -55,6 +55,8 @@ typedef struct INPparseNode {
     int usecnt;
 } INPparseNode;
 
+/* A debugging function */
+void INPptPrint(char *str, IFparseTree * ptree);
 
 /* FIXME, less public
  *   and replace with static inline functions for better type check
diff --git a/src/spicelib/parser/ifeval.c b/src/spicelib/parser/ifeval.c
index a48003551..adba91e4e 100644
--- a/src/spicelib/parser/ifeval.c
+++ b/src/spicelib/parser/ifeval.c
@@ -38,12 +38,32 @@ IFeval(IFparseTree * tree, double gmin, double *result, double *vals,
 	printf("\tvar%d = %lg\n", i, vals[i]);
 #endif
 
-    if ((err = PTeval(myTree->tree, gmin, result, vals)) != OK)
-	return (err);
+    if ((err = PTeval(myTree->tree, gmin, result, vals)) != OK) {
+        if (ft_ngdebug) {
+            INPptPrint("calling PTeval, tree = ", tree);
+            printf("values:");
+            for (i = 0; i < myTree->p.numVars; i++)
+	        printf("\tvar%d = %lg\n", i, vals[i]);
+        }
+        if (ft_stricterror)
+            controlled_exit(EXIT_BAD);
+        else
+            return (err);
+    }
 
     for (i = 0; i < myTree->p.numVars; i++)
-	if ((err = PTeval(myTree->derivs[i], gmin, &derivs[i], vals)) !=
-	    OK) return (err);
+        if ((err = PTeval(myTree->derivs[i], gmin, &derivs[i], vals)) != OK) {
+            if (ft_ngdebug) {
+                INPptPrint("calling PTeval, tree = ", tree);
+                printf("results: function = %lg\n", *result);
+                for (i = 0; i < myTree->p.numVars; i++)
+	                printf("\td / d var%d = %lg\n", i, derivs[i]);
+            }
+            if (ft_stricterror)
+                controlled_exit(EXIT_BAD);
+            else
+                return (err);
+        }
 
 #ifdef TRACE
     printf("results: function = %lg\n", *result);
diff --git a/src/spicelib/parser/inpptree.c b/src/spicelib/parser/inpptree.c
index 9c5ef0781..944b514cd 100644
--- a/src/spicelib/parser/inpptree.c
+++ b/src/spicelib/parser/inpptree.c
@@ -1383,8 +1383,6 @@ void free_tree(INPparseNode *pt)
 }
 
 
-#ifdef TRACE
-
 /* Debugging stuff. */
 
 void printTree(INPparseNode *);
@@ -1497,4 +1495,3 @@ void printTree(INPparseNode * pt)
     return;
 }
 
-#endif