diff --git a/src/maths/KLU/klusmp.c b/src/maths/KLU/klusmp.c
index 8985d440c..174dee419 100644
--- a/src/maths/KLU/klusmp.c
+++ b/src/maths/KLU/klusmp.c
@@ -10,6 +10,7 @@
 #include "ngspice/spmatrix.h"
 #include "../sparse/spdefs.h"
 #include "ngspice/smpdefs.h"
+#include "ngspice/fteext.h"
 
 #if defined (_MSC_VER)
 extern double scalbn(double, int);
@@ -535,9 +536,11 @@ SMPcLUfac (SMPmatrix *Matrix, double PivTol)
         if (ret == 0)
         {
             if (Matrix->SMPkluMatrix->KLUmatrixCommon->status == KLU_SINGULAR) {
-                fprintf (stderr, "Warning (ReFactor Complex): KLU Matrix is SINGULAR\n") ;
-                fprintf (stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank) ;
-                fprintf (stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1) ;
+                if (ft_ngdebug) {
+                    fprintf(stderr, "Warning (ReFactor Complex): KLU Matrix is SINGULAR\n");
+                    fprintf(stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank);
+                    fprintf(stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1);
+                }
                 return E_SINGULAR ;
             }
             if (Matrix->SMPkluMatrix->KLUmatrixCommon == NULL) {
@@ -590,9 +593,11 @@ SMPluFac (SMPmatrix *Matrix, double PivTol, double Gmin)
         if (ret == 0)
         {
             if (Matrix->SMPkluMatrix->KLUmatrixCommon->status == KLU_SINGULAR) {
-                fprintf (stderr, "Warning (ReFactor): KLU Matrix is SINGULAR\n") ;
-                fprintf (stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank) ;
-                fprintf (stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1) ;
+                if (ft_ngdebug) {
+                    fprintf(stderr, "Warning (ReFactor): KLU Matrix is SINGULAR\n");
+                    fprintf(stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank);
+                    fprintf(stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1);
+                }
                 return E_SINGULAR ;
             }
             if (Matrix->SMPkluMatrix->KLUmatrixCommon == NULL) {
@@ -655,9 +660,11 @@ SMPluFacKLUforCIDER (SMPmatrix *Matrix)
         if (ret == 0)
         {
             if (Matrix->SMPkluMatrix->KLUmatrixCommon->status == KLU_SINGULAR) {
-                fprintf (stderr, "Warning (ReFactor for CIDER): KLU Matrix is SINGULAR\n") ;
-                fprintf (stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank) ;
-                fprintf (stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1) ;
+                if (ft_ngdebug) {
+                    fprintf(stderr, "Warning (ReFactor for CIDER): KLU Matrix is SINGULAR\n");
+                    fprintf(stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank);
+                    fprintf(stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1);
+                }
                 return E_SINGULAR ;
             }
             if (Matrix->SMPkluMatrix->KLUmatrixCommon == NULL) {
@@ -707,9 +714,11 @@ SMPcReorder (SMPmatrix *Matrix, double PivTol, double PivRel, int *NumSwaps)
         if (Matrix->SMPkluMatrix->KLUmatrixNumeric == NULL)
         {
             if (Matrix->SMPkluMatrix->KLUmatrixCommon->status == KLU_SINGULAR) {
-                fprintf (stderr, "Warning (Factor Complex): KLU Matrix is SINGULAR\n") ;
-                fprintf (stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank) ;
-                fprintf (stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1) ;
+                if (ft_ngdebug) {
+                    fprintf(stderr, "Warning (Factor Complex): KLU Matrix is SINGULAR\n");
+                    fprintf(stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank);
+                    fprintf(stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1);
+                }
                 return E_SINGULAR ;
             }
             if (Matrix->SMPkluMatrix->KLUmatrixCommon == NULL) {
@@ -765,9 +774,11 @@ SMPreorder (SMPmatrix *Matrix, double PivTol, double PivRel, double Gmin)
         if (Matrix->SMPkluMatrix->KLUmatrixNumeric == NULL)
         {
             if (Matrix->SMPkluMatrix->KLUmatrixCommon->status == KLU_SINGULAR) {
-                fprintf (stderr, "Warning (Factor): KLU Matrix is SINGULAR\n") ;
-                fprintf (stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank) ;
-                fprintf (stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1) ;
+                if (ft_ngdebug) {
+                    fprintf(stderr, "Warning (Factor): KLU Matrix is SINGULAR\n");
+                    fprintf(stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank);
+                    fprintf(stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1);
+                }
                 return E_SINGULAR ;
             }
             if (Matrix->SMPkluMatrix->KLUmatrixCommon == NULL) {
@@ -835,9 +846,11 @@ SMPreorderKLUforCIDER (SMPmatrix *Matrix)
         if (Matrix->SMPkluMatrix->KLUmatrixNumeric == NULL)
         {
             if (Matrix->SMPkluMatrix->KLUmatrixCommon->status == KLU_SINGULAR) {
-                fprintf (stderr, "Warning (Factor for CIDER): KLU Matrix is SINGULAR\n") ;
-                fprintf (stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank) ;
-                fprintf (stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1) ;
+                if (ft_ngdebug) {
+                    fprintf(stderr, "Warning (Factor for CIDER): KLU Matrix is SINGULAR\n");
+                    fprintf(stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank);
+                    fprintf(stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1);
+                }
                 return E_SINGULAR ;
             }
             if (Matrix->SMPkluMatrix->KLUmatrixCommon == NULL) {
@@ -960,9 +973,12 @@ SMPsolve (SMPmatrix *Matrix, double RHS[], double Spare[])
         if (ret == 0)
         {
             if (Matrix->SMPkluMatrix->KLUmatrixCommon->status == KLU_SINGULAR) {
-                fprintf (stderr, "Warning (Solve): KLU Matrix is SINGULAR\n") ;
-                fprintf (stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank) ;
-                fprintf (stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1) ;
+                if (ft_ngdebug) {
+                    fprintf(stderr, "Warning (Solve): KLU Matrix is SINGULAR\n");
+                    fprintf(stderr, "  Numerical Rank: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->numerical_rank);
+                    fprintf(stderr, "  Singular Node: %d\n", Matrix->SMPkluMatrix->KLUmatrixCommon->singular_col + 1);
+                }
+                /* FIXME: Do we need a 'return E_SINGULAR' here? */
             }
             if (Matrix->SMPkluMatrix->KLUmatrixCommon == NULL) {
                 fprintf (stderr, "Error (Solve): KLUcommon object is NULL. A problem occurred\n") ;
diff --git a/src/maths/ni/niiter.c b/src/maths/ni/niiter.c
index bf945f3f6..941859b4e 100644
--- a/src/maths/ni/niiter.c
+++ b/src/maths/ni/niiter.c
@@ -166,8 +166,8 @@ NIiter(CKTcircuit *ckt, int maxIter)
                      * This is my mod with KLU. It saves run-time, but also the system at the next iteration may be different.
                      * How do we guarantee that the system is the same at the next iteration? So, the original SPARSE version below sounds like a bug.
                      */
-
-                    fprintf (stderr, "Warning: KLU ReFactor failed. Factoring again...\n") ;
+                    if (ft_ngdebug)
+                        fprintf (stderr, "Warning: KLU ReFactor failed. Factoring again...\n") ;
                     ckt->CKTniState |= NISHOULDREORDER;
                     ckt->CKTmatrix->SMPkluMatrix->KLUloadDiagGmin = 0 ;
                     error = SMPreorder(ckt->CKTmatrix, ckt->CKTpivotAbsTol, ckt->CKTpivotRelTol, ckt->CKTdiagGmin);