diff --git a/src/mac/app.cpp b/src/mac/app.cpp
index 57a0a7a787..baa2127bbf 100644
--- a/src/mac/app.cpp
+++ b/src/mac/app.cpp
@@ -609,7 +609,7 @@ bool wxApp::Initialize(int& argc, wxChar **argv)
     if ( argc > 1 )
     {
         static const wxChar *ARG_PSN = _T("-psn_");
-        if ( wxStrncmp(argv[1], ARG_PSN, strlen(ARG_PSN)) == 0 )
+        if ( wxStrncmp(argv[1], ARG_PSN, wxStrlen(ARG_PSN)) == 0 )
         {
             // remove this argument
             --argc;
diff --git a/src/mac/carbon/app.cpp b/src/mac/carbon/app.cpp
index 57a0a7a787..baa2127bbf 100644
--- a/src/mac/carbon/app.cpp
+++ b/src/mac/carbon/app.cpp
@@ -609,7 +609,7 @@ bool wxApp::Initialize(int& argc, wxChar **argv)
     if ( argc > 1 )
     {
         static const wxChar *ARG_PSN = _T("-psn_");
-        if ( wxStrncmp(argv[1], ARG_PSN, strlen(ARG_PSN)) == 0 )
+        if ( wxStrncmp(argv[1], ARG_PSN, wxStrlen(ARG_PSN)) == 0 )
         {
             // remove this argument
             --argc;