diff --git a/src/efinix.cpp b/src/efinix.cpp
index 267eeb8..aad7123 100644
--- a/src/efinix.cpp
+++ b/src/efinix.cpp
@@ -469,6 +469,7 @@ int Efinix::spi_wait(uint8_t cmd, uint8_t mask, uint8_t cond,
 			uint32_t timeout, bool verbose)
 {
 	uint8_t rx[2], dummy[2], tmp;
+	memset(dummy, 0xff, sizeof(dummy));
 	uint8_t tx = EfinixHexParser::reverseByte(cmd);
 	uint32_t count = 0;
 
diff --git a/src/ice40.cpp b/src/ice40.cpp
index dbd8ccb..cd873a0 100644
--- a/src/ice40.cpp
+++ b/src/ice40.cpp
@@ -89,7 +89,8 @@ bool Ice40::program_cram(const uint8_t *data, uint32_t length)
 	progress.done();
 
 	/* send 48 to 100 dummy bits */
-	uint8_t dummy[12] = {0xff};
+	uint8_t dummy[12];
+	memset(dummy, 0xff, sizeof(dummy));
 	_spi->spi_put(dummy, NULL, 12);
 
 	/* wait CDONE */
diff --git a/src/xilinx.cpp b/src/xilinx.cpp
index b2724e2..bf84686 100644
--- a/src/xilinx.cpp
+++ b/src/xilinx.cpp
@@ -1577,7 +1577,8 @@ int Xilinx::spi_wait(uint8_t cmd, uint8_t mask, uint8_t cond,
 			uint32_t timeout, bool verbose)
 {
 	uint8_t rx[2];
-	uint8_t dummy[2] = {0xff};
+	uint8_t dummy[2];
+	memset(dummy, 0xff, sizeof(dummy));
 	uint8_t tmp;
 	uint8_t tx = McsParser::reverseByte(cmd);
 	uint32_t count = 0;