diff --git a/src/mac/carbon/spinbutt.cpp b/src/mac/carbon/spinbutt.cpp
index fc4e5e5888..283d6bc262 100644
--- a/src/mac/carbon/spinbutt.cpp
+++ b/src/mac/carbon/spinbutt.cpp
@@ -161,7 +161,7 @@ void wxSpinButton::MacHandleControlClick( ControlHandle control , SInt16 control
 
 wxSize wxSpinButton::DoGetBestSize() const
 {
-    if ( (GetWindowStyle() & wxSP_VERTICAL) != 0 )
+    if ( (GetWindowStyle() & wxSP_HORIZONTAL) == 0 )
     {
         // vertical control
         return wxSize(16,
diff --git a/src/mac/spinbutt.cpp b/src/mac/spinbutt.cpp
index fc4e5e5888..283d6bc262 100644
--- a/src/mac/spinbutt.cpp
+++ b/src/mac/spinbutt.cpp
@@ -161,7 +161,7 @@ void wxSpinButton::MacHandleControlClick( ControlHandle control , SInt16 control
 
 wxSize wxSpinButton::DoGetBestSize() const
 {
-    if ( (GetWindowStyle() & wxSP_VERTICAL) != 0 )
+    if ( (GetWindowStyle() & wxSP_HORIZONTAL) == 0 )
     {
         // vertical control
         return wxSize(16,