diff --git a/libfreerdp/common/addin.c b/libfreerdp/common/addin.c
index af608bb07..5a76839e4 100644
--- a/libfreerdp/common/addin.c
+++ b/libfreerdp/common/addin.c
@@ -304,11 +304,11 @@ PVIRTUALCHANNELENTRY freerdp_load_dynamic_channel_addin_entry(LPCSTR pszName, LP
 
 	{
 		LPCSTR pszExtension = PathGetSharedLibraryExtensionA(0);
-		LPCSTR pszPrefix = FREERDP_SHARED_LIBRARY_PREFIX;
+		const char pszPrefix[] = FREERDP_SHARED_LIBRARY_PREFIX;
 		int rc = 0;
 
 		if (pszPrefix)
-			cchFileName += strnlen(pszPrefix, MAX_PATH);
+			cchFileName += strnlen(pszPrefix, ARRAYSIZE(pszPrefix));
 		if (pszExtension)
 			cchFileName += strnlen(pszExtension, MAX_PATH) + 1;
 		LPSTR tmp = calloc(cchFileName, sizeof(CHAR));