diff --git a/src/modbus.c b/src/modbus.c
index d728977..d075522 100644
--- a/src/modbus.c
+++ b/src/modbus.c
@@ -1290,7 +1290,7 @@ int modbus_write_registers(modbus_t *ctx, int addr, int nb, const uint16_t *src)
     return rc;
 }
 
-int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and, uint16_t or)
+int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and_mask, uint16_t or_mask)
 {
     int rc;
     int req_length;
@@ -1301,10 +1301,10 @@ int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and, uint16_t o
     /* HACKISH, count is not used */
     req_length -=2;
 
-    req[req_length++] = and >> 8;
-    req[req_length++] = and & 0x00ff;
-    req[req_length++] = or >> 8;
-    req[req_length++] = or & 0x00ff;
+    req[req_length++] = and_mask >> 8;
+    req[req_length++] = and_mask & 0x00ff;
+    req[req_length++] = or_mask >> 8;
+    req[req_length++] = or_mask & 0x00ff;
 
     rc = send_msg(ctx, req, req_length);
     if (rc > 0) {
diff --git a/src/modbus.h b/src/modbus.h
index 964a647..70a011f 100644
--- a/src/modbus.h
+++ b/src/modbus.h
@@ -185,7 +185,7 @@ EXPORT int modbus_write_bit(modbus_t *ctx, int coil_addr, int status);
 EXPORT int modbus_write_register(modbus_t *ctx, int reg_addr, int value);
 EXPORT int modbus_write_bits(modbus_t *ctx, int addr, int nb, const uint8_t *data);
 EXPORT int modbus_write_registers(modbus_t *ctx, int addr, int nb, const uint16_t *data);
-EXPORT int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and, uint16_t or);
+EXPORT int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and_mask, uint16_t or_mask);
 EXPORT int modbus_write_and_read_registers(modbus_t *ctx, int write_addr, int write_nb,
                                            const uint16_t *src, int read_addr, int read_nb,
                                            uint16_t *dest);