diff --git a/src/target/arm9tdmi.c b/src/target/arm9tdmi.c
index 805330f25..3bacfaefd 100644
--- a/src/target/arm9tdmi.c
+++ b/src/target/arm9tdmi.c
@@ -57,7 +57,7 @@ static const struct arm9tdmi_vector {
 	{"dabt", ARM9TDMI_DABT_VECTOR},
 	{"irq", ARM9TDMI_IRQ_VECTOR},
 	{"fiq", ARM9TDMI_FIQ_VECTOR},
-	{0, 0},
+	{NULL, 0},
 };
 
 int arm9tdmi_examine_debug_reason(struct target *target)
diff --git a/src/target/armv8_dpm.c b/src/target/armv8_dpm.c
index fcd4d5971..d1eefe5b3 100644
--- a/src/target/armv8_dpm.c
+++ b/src/target/armv8_dpm.c
@@ -274,7 +274,7 @@ static int dpmv8_instr_write_data_dcc(struct arm_dpm *dpm,
 	if (retval != ERROR_OK)
 		return retval;
 
-	return dpmv8_exec_opcode(dpm, opcode, 0);
+	return dpmv8_exec_opcode(dpm, opcode, NULL);
 }
 
 static int dpmv8_instr_write_data_dcc_64(struct arm_dpm *dpm,
@@ -287,7 +287,7 @@ static int dpmv8_instr_write_data_dcc_64(struct arm_dpm *dpm,
 	if (retval != ERROR_OK)
 		return retval;
 
-	return dpmv8_exec_opcode(dpm, opcode, 0);
+	return dpmv8_exec_opcode(dpm, opcode, NULL);
 }
 
 static int dpmv8_instr_write_data_r0(struct arm_dpm *dpm,
diff --git a/src/target/dsp563xx_once.c b/src/target/dsp563xx_once.c
index 22445067a..866f33152 100644
--- a/src/target/dsp563xx_once.c
+++ b/src/target/dsp563xx_once.c
@@ -60,7 +60,7 @@ static inline int dsp563xx_once_ir_exec(struct jtag_tap *tap, int flush, uint8_t
 {
 	int err;
 
-	err = dsp563xx_write_dr_u8(tap, 0, instr | (ex << 5) | (go << 6) | (rw << 7), 8, 0);
+	err = dsp563xx_write_dr_u8(tap, NULL, instr | (ex << 5) | (go << 6) | (rw << 7), 8, 0);
 	if (err != ERROR_OK)
 		return err;
 	if (flush)
@@ -226,7 +226,7 @@ int dsp563xx_once_reg_write(struct jtag_tap *tap, int flush, uint8_t reg, uint32
 	err = dsp563xx_once_ir_exec(tap, flush, reg, 0, 0, 0);
 	if (err != ERROR_OK)
 		return err;
-	err = dsp563xx_write_dr_u32(tap, 0x00, data, 24, 0);
+	err = dsp563xx_write_dr_u32(tap, NULL, data, 24, 0);
 	if (err != ERROR_OK)
 		return err;
 	if (flush)
@@ -242,7 +242,7 @@ int dsp563xx_once_execute_sw_ir(struct jtag_tap *tap, int flush, uint32_t opcode
 	err = dsp563xx_once_ir_exec(tap, flush, DSP563XX_ONCE_OPDBR, 0, 1, 0);
 	if (err != ERROR_OK)
 		return err;
-	err = dsp563xx_write_dr_u32(tap, 0, opcode, 24, 0);
+	err = dsp563xx_write_dr_u32(tap, NULL, opcode, 24, 0);
 	if (err != ERROR_OK)
 		return err;
 	if (flush)
@@ -258,7 +258,7 @@ int dsp563xx_once_execute_dw_ir(struct jtag_tap *tap, int flush, uint32_t opcode
 	err = dsp563xx_once_ir_exec(tap, flush, DSP563XX_ONCE_OPDBR, 0, 0, 0);
 	if (err != ERROR_OK)
 		return err;
-	err = dsp563xx_write_dr_u32(tap, 0, opcode, 24, 0);
+	err = dsp563xx_write_dr_u32(tap, NULL, opcode, 24, 0);
 	if (err != ERROR_OK)
 		return err;
 	if (flush) {
@@ -270,7 +270,7 @@ int dsp563xx_once_execute_dw_ir(struct jtag_tap *tap, int flush, uint32_t opcode
 	err = dsp563xx_once_ir_exec(tap, flush, DSP563XX_ONCE_OPDBR, 0, 1, 0);
 	if (err != ERROR_OK)
 		return err;
-	err = dsp563xx_write_dr_u32(tap, 0, operand, 24, 0);
+	err = dsp563xx_write_dr_u32(tap, NULL, operand, 24, 0);
 	if (err != ERROR_OK)
 		return err;
 	if (flush) {
diff --git a/src/target/xtensa/xtensa.c b/src/target/xtensa/xtensa.c
index fcd00487c..63ffefce7 100644
--- a/src/target/xtensa/xtensa.c
+++ b/src/target/xtensa/xtensa.c
@@ -410,7 +410,7 @@ static int xtensa_core_reg_get(struct reg *reg)
 		return ERROR_TARGET_NOT_HALTED;
 	if (!reg->exist) {
 		if (strncmp(reg->name, "?0x", 3) == 0) {
-			unsigned int regnum = strtoul(reg->name + 1, 0, 0);
+			unsigned int regnum = strtoul(reg->name + 1, NULL, 0);
 			LOG_WARNING("Read unknown register 0x%04x ignored", regnum);
 			return ERROR_OK;
 		}
@@ -430,7 +430,7 @@ static int xtensa_core_reg_set(struct reg *reg, uint8_t *buf)
 
 	if (!reg->exist) {
 		if (strncmp(reg->name, "?0x", 3) == 0) {
-			unsigned int regnum = strtoul(reg->name + 1, 0, 0);
+			unsigned int regnum = strtoul(reg->name + 1, NULL, 0);
 			LOG_WARNING("Write unknown register 0x%04x ignored", regnum);
 			return ERROR_OK;
 		}