diff --git a/include/wx/fontutil.h b/include/wx/fontutil.h
index 33e9313755..aee4cf4fd5 100644
--- a/include/wx/fontutil.h
+++ b/include/wx/fontutil.h
@@ -285,6 +285,17 @@ public:
     void SetFamily(wxFontFamily family);
     void SetEncoding(wxFontEncoding encoding);
 
+    // Helper used in many ports: use the normal font size if the input is
+    // negative, as we handle -1 as meaning this for compatibility.
+    void SetSizeOrDefault(float size)
+    {
+        SetFractionalPointSize
+        (
+            size < 0 ? wxNORMAL_FONT->GetFractionalPointSize()
+                     : size
+        );
+    }
+
     // sets the first facename in the given array which is found
     // to be valid. If no valid facename is given, sets the
     // first valid facename returned by wxFontEnumerator::GetFacenames().
diff --git a/src/gtk/font.cpp b/src/gtk/font.cpp
index 7ad3e9ec11..e8bf634526 100644
--- a/src/gtk/font.cpp
+++ b/src/gtk/font.cpp
@@ -133,11 +133,7 @@ void wxFontRefData::Init(float pointSize,
     }
 
     SetStyle( style );
-    m_nativeFontInfo.SetFractionalPointSize
-                     (
-                        pointSize < 0 ? static_cast<float>(wxDEFAULT_FONT_SIZE)
-                                      : pointSize
-                     );
+    m_nativeFontInfo.SetSizeOrDefault(pointSize);
     SetNumericWeight( weight );
     SetUnderlined( underlined );
     SetStrikethrough( strikethrough );
diff --git a/src/msw/font.cpp b/src/msw/font.cpp
index a2111bcdc9..668873fc14 100644
--- a/src/msw/font.cpp
+++ b/src/msw/font.cpp
@@ -362,12 +362,7 @@ void wxFontRefData::Init(float pointSize,
     }
     else
     {
-        m_nativeFontInfo.SetFractionalPointSize
-                         (
-                            pointSize < 0
-                                ? wxNORMAL_FONT->GetPointSize()
-                                : pointSize
-                        );
+        m_nativeFontInfo.SetSizeOrDefault(pointSize);
     }
 
     SetStyle(style);
diff --git a/src/osx/carbon/font.cpp b/src/osx/carbon/font.cpp
index 106ab44902..07d5968aef 100644
--- a/src/osx/carbon/font.cpp
+++ b/src/osx/carbon/font.cpp
@@ -301,7 +301,7 @@ void wxFontRefData::Init(float size,
     else
         SetFamily(family);
 
-    SetFractionalPointSize(size < 0 ? wxNORMAL_FONT->GetFractionalPointSize() : size);
+    m_info.SetSizeOrDefault(size);
     SetNumericWeight(weight);
     SetStyle(style);
     SetUnderlined(underlined);