diff --git a/SSD1306Ascii.cpp b/SSD1306Ascii.cpp
index e125eff..bc13270 100644
--- a/SSD1306Ascii.cpp
+++ b/SSD1306Ascii.cpp
@@ -73,6 +73,8 @@ void SSD1306Ascii::setCursor(uint8_t col, uint8_t row) {
 //------------------------------------------------------------------------------
 void SSD1306Ascii::setFont(const uint8_t* font) {
   m_font = font;
+  fontFirstChar = readFontByte(m_font + FONT_FIRST_CHAR);
+  fontCharCount = readFontByte(m_font + FONT_CHAR_COUNT); 
 }
 //------------------------------------------------------------------------------
 void SSD1306Ascii::setRow(uint8_t row) {
@@ -101,10 +103,6 @@ size_t SSD1306Ascii::write(uint8_t ch) {
     return 0;
   }
   const uint8_t* base = m_font + FONT_WIDTH_TABLE;
-  const uint8_t letterSpacing = 1;
-  uint8_t fontFirstChar = readFontByte(m_font + FONT_FIRST_CHAR);
-  uint8_t fontCharCount = readFontByte(m_font + FONT_CHAR_COUNT); 
-  uint8_t fontWidth = readFontByte(m_font + FONT_WIDTH);
 
   if (ch < fontFirstChar || ch >= (fontFirstChar + fontCharCount)) return 0;
   ch -= fontFirstChar;
diff --git a/SSD1306Ascii.h b/SSD1306Ascii.h
index 16a3556..84dc390 100644
--- a/SSD1306Ascii.h
+++ b/SSD1306Ascii.h
@@ -195,6 +195,13 @@ class SSD1306Ascii : public Print {
   uint8_t m_displayHeight;  // Display height.
   uint8_t m_colOffset;      // Column offset RAM to SEG.
   const uint8_t* m_font = nullptr;  // Current font.
+
+  // Only fixed size 5x7 fonts in a 6x8 cell are supported.
+  const int fontWidth = 5;
+  const int fontHeight = 7;
+  const uint8_t letterSpacing = 1;
+  uint8_t fontFirstChar;
+  uint8_t fontCharCount;
 };