diff --git a/src/maths/cmaths/cmath4.c b/src/maths/cmaths/cmath4.c
index 0f9078950..50d772761 100644
--- a/src/maths/cmaths/cmath4.c
+++ b/src/maths/cmaths/cmath4.c
@@ -940,6 +940,10 @@ cx_ifft(void *data, short int type, int length, int *newlength, short int *newty
         in[i][0] = indata[i].cx_real;
         in[i][1] = indata[i].cx_imag;
     }
+    for (i = length; i < tpts; i++) {
+        in[i][0] = 0.0;
+        in[i][1] = 0.0;
+    }
 
     plan_backward = fftw_plan_dft_1d(tpts, in, out, FFTW_BACKWARD, FFTW_ESTIMATE);