diff --git a/apps/plugin.h b/apps/plugin.h
index 461966e8bd..d332a0d004 100644
--- a/apps/plugin.h
+++ b/apps/plugin.h
@@ -555,7 +555,7 @@ struct plugin_api {
     int (*mas_codec_readreg)(int reg);
     void (*i2c_begin)(void);
     void (*i2c_end)(void);
-    int  (*i2c_write)(int address, unsigned char* buf, int count );
+    int  (*i2c_write)(int address, const unsigned char* buf, int count );
 #endif
 #endif
 
diff --git a/firmware/target/arm/i2c-telechips.c b/firmware/target/arm/i2c-telechips.c
index 8e5db2f26f..bf975f66f0 100644
--- a/firmware/target/arm/i2c-telechips.c
+++ b/firmware/target/arm/i2c-telechips.c
@@ -138,7 +138,7 @@ int i2c_getack(void)
 }
 
 /* device = 8 bit slave address */
-int i2c_write(int device, unsigned char* buf, int count )
+int i2c_write(int device, const unsigned char* buf, int count )
 {
     int i = 0;
     mutex_lock(&i2c_mtx);