diff --git a/dlls/msi/appsearch.c b/dlls/msi/appsearch.c
index ea2f7cff003..8db9cb9def6 100644
--- a/dlls/msi/appsearch.c
+++ b/dlls/msi/appsearch.c
@@ -474,7 +474,7 @@ static void ACTION_ExpandAnyPath(MSIPACKAGE *package, WCHAR *src, WCHAR *dst,
  * Return ERROR_SUCCESS in case of success (whether or not the file matches),
  * something else if an install-halting error occurs.
  */
-static UINT ACTION_FileVersionMatches(MSISIGNATURE *sig, LPCWSTR filePath,
+static UINT ACTION_FileVersionMatches(const MSISIGNATURE *sig, LPCWSTR filePath,
  BOOL *matches)
 {
     UINT rc = ERROR_SUCCESS;
@@ -549,8 +549,8 @@ static UINT ACTION_FileVersionMatches(MSISIGNATURE *sig, LPCWSTR filePath,
  * Return ERROR_SUCCESS in case of success (whether or not the file matches),
  * something else if an install-halting error occurs.
  */
-static UINT ACTION_FileMatchesSig(MSISIGNATURE *sig,
- LPWIN32_FIND_DATAW findData, LPCWSTR fullFilePath, BOOL *matches)
+static UINT ACTION_FileMatchesSig(const MSISIGNATURE *sig,
+ const WIN32_FIND_DATAW *findData, LPCWSTR fullFilePath, BOOL *matches)
 {
     UINT rc = ERROR_SUCCESS;
 
diff --git a/dlls/msi/classes.c b/dlls/msi/classes.c
index e2bb34cf4c4..92c333d5b6a 100644
--- a/dlls/msi/classes.c
+++ b/dlls/msi/classes.c
@@ -735,7 +735,7 @@ static void mark_mime_for_install( MSIMIME *mime )
     mime->InstallMe = TRUE;
 }
 
-static UINT register_appid(MSIAPPID *appid, LPCWSTR app )
+static UINT register_appid(const MSIAPPID *appid, LPCWSTR app )
 {
     static const WCHAR szAppID[] = { 'A','p','p','I','D',0 };
     static const WCHAR szRemoteServerName[] =
@@ -965,7 +965,7 @@ UINT ACTION_RegisterClassInfo(MSIPACKAGE *package)
     return rc;
 }
 
-static LPCWSTR get_clsid_of_progid( MSIPROGID *progid )
+static LPCWSTR get_clsid_of_progid( const MSIPROGID *progid )
 {
     while (progid)
     {
@@ -976,7 +976,7 @@ static LPCWSTR get_clsid_of_progid( MSIPROGID *progid )
     return NULL;
 }
 
-static UINT register_progid( MSIPROGID* progid )
+static UINT register_progid( const MSIPROGID* progid )
 {
     static const WCHAR szCLSID[] = { 'C','L','S','I','D',0 };
     static const WCHAR szDefaultIcon[] =
@@ -1048,7 +1048,7 @@ UINT ACTION_RegisterProgIdInfo(MSIPACKAGE *package)
 }
 
 static UINT register_verb(MSIPACKAGE *package, LPCWSTR progid, 
-                MSICOMPONENT* component, MSIEXTENSION* extension,
+                MSICOMPONENT* component, const MSIEXTENSION* extension,
                 MSIVERB* verb, INT* Sequence )
 {
     LPWSTR keyname;
diff --git a/dlls/msi/cond.y b/dlls/msi/cond.y
index 9cfb00114fa..ee42edebb4e 100644
--- a/dlls/msi/cond.y
+++ b/dlls/msi/cond.y
@@ -56,8 +56,8 @@ struct cond_str {
     INT len;
 };
 
-static LPWSTR COND_GetString( struct cond_str *str );
-static LPWSTR COND_GetLiteral( struct cond_str *str );
+static LPWSTR COND_GetString( const struct cond_str *str );
+static LPWSTR COND_GetLiteral( const struct cond_str *str );
 static int cond_lex( void *COND_lval, COND_input *info);
 static const WCHAR szEmpty[] = { 0 };
 
@@ -678,7 +678,7 @@ static int cond_lex( void *COND_lval, COND_input *cond )
     return rc;
 }
 
-static LPWSTR COND_GetString( struct cond_str *str )
+static LPWSTR COND_GetString( const struct cond_str *str )
 {
     LPWSTR ret;
 
@@ -692,7 +692,7 @@ static LPWSTR COND_GetString( struct cond_str *str )
     return ret;
 }
 
-static LPWSTR COND_GetLiteral( struct cond_str *str )
+static LPWSTR COND_GetLiteral( const struct cond_str *str )
 {
     LPWSTR ret;
 
diff --git a/dlls/msi/custom.c b/dlls/msi/custom.c
index 0216f0310f6..e5162568a96 100644
--- a/dlls/msi/custom.c
+++ b/dlls/msi/custom.c
@@ -124,7 +124,7 @@ static BOOL check_execution_scheduling_options(MSIPACKAGE *package, LPCWSTR acti
 /* stores the CustomActionData before the action:
  *     [CustomActionData]Action
  */
-static LPWSTR msi_get_deferred_action(LPCWSTR action, LPWSTR actiondata)
+static LPWSTR msi_get_deferred_action(LPCWSTR action, LPCWSTR actiondata)
 {
     LPWSTR deferred;
     DWORD len;
@@ -1016,7 +1016,7 @@ static UINT HANDLE_CustomType34(MSIPACKAGE *package, LPCWSTR source,
     return wait_process_handle(package, type, info.hProcess, action);
 }
 
-static DWORD WINAPI ACTION_CallScript( const LPGUID guid )
+static DWORD WINAPI ACTION_CallScript( const GUID *guid )
 {
     msi_custom_action_info *info;
     MSIHANDLE hPackage;
@@ -1235,7 +1235,7 @@ static UINT HANDLE_CustomType53_54(MSIPACKAGE *package, LPCWSTR source,
     return wait_thread_handle( info );
 }
 
-void ACTION_FinishCustomActions(MSIPACKAGE* package)
+void ACTION_FinishCustomActions(const MSIPACKAGE* package)
 {
     struct list *item;
     HANDLE *wait_handles;
diff --git a/dlls/msi/msipriv.h b/dlls/msi/msipriv.h
index f8f1d3de2c0..2d05d76d0be 100644
--- a/dlls/msi/msipriv.h
+++ b/dlls/msi/msipriv.h
@@ -726,7 +726,7 @@ extern HINSTANCE msi_hInstance;
 /* action related functions */
 extern UINT ACTION_PerformAction(MSIPACKAGE *package, const WCHAR *action, BOOL force);
 extern UINT ACTION_PerformUIAction(MSIPACKAGE *package, const WCHAR *action);
-extern void ACTION_FinishCustomActions( MSIPACKAGE* package);
+extern void ACTION_FinishCustomActions( const MSIPACKAGE* package);
 extern UINT ACTION_CustomAction(MSIPACKAGE *package,const WCHAR *action, BOOL execute);
 
 static inline void msi_feature_set_state( MSIFEATURE *feature, INSTALLSTATE state )