diff --git a/lib/signal/bandpass2.c b/lib/signal/bandpass2.c
index ce2efa1..6ea2244 100644
--- a/lib/signal/bandpass2.c
+++ b/lib/signal/bandpass2.c
@@ -92,7 +92,7 @@ int rtbuf_signal_bandpass2 (s_rtbuf *rtb)
s_rtbuf_signal_fun qfactor;
s_rtbuf_signal_bandpass2_data *data;
unsigned int i = 0;
- const double sqrt2_3 = sqrt2_2 * M_SQRT2;
+ const double sqrt2_3 = M_SQRT2 * sqrt2_2;
const double sqrt2_5 = sqrt2_3 * sqrt2_2;
const double sqrt2_7 = sqrt2_5 * sqrt2_2;
const double sqrt2_9 = sqrt2_7 * sqrt2_2;