diff --git a/src/librtlsdr.c b/src/librtlsdr.c
index 87efc38..9e6b56e 100644
--- a/src/librtlsdr.c
+++ b/src/librtlsdr.c
@@ -537,7 +537,7 @@ void rtlsdr_init_baseband(rtlsdr_dev_t *dev)
 
 	/* default FIR coefficients used for DAB/FM by the Windows driver,
 	 * the DVB driver uses different ones */
-	uint8_t fir_coeff[] = {
+	const uint8_t fir_coeff[] = {
 		0xca, 0xdc, 0xd7, 0xd8, 0xe0, 0xf2, 0x0e, 0x35, 0x06, 0x50,
 		0x9c, 0x0d, 0x71, 0x11, 0x14, 0x71, 0x74, 0x19, 0x41, 0xa5,
 	};