diff --git a/Source/codec.cpp b/Source/codec.cpp
index d8019fd8f..c25929e8e 100644
--- a/Source/codec.cpp
+++ b/Source/codec.cpp
@@ -63,7 +63,7 @@ error:
 	return 0;
 }
 
-void codec_init_key(int unused, char *pszPassword)
+void codec_init_key(int unused, const char *pszPassword)
 {
 	char key[136]; // last 64 bytes are the SHA1
 	uint32_t rand_state = 0x7058;
diff --git a/Source/codec.h b/Source/codec.h
index 859e366d1..a36984647 100644
--- a/Source/codec.h
+++ b/Source/codec.h
@@ -13,7 +13,7 @@ extern "C" {
 #endif
 
 int codec_decode(BYTE *pbSrcDst, DWORD size, const  char *pszPassword);
-void codec_init_key(int unused, char *pszPassword);
+void codec_init_key(int unused, const char *pszPassword);
 DWORD codec_get_encoded_len(DWORD dwSrcBytes);
 void codec_encode(BYTE *pbSrcDst, DWORD size, int size_64, const char *pszPassword);