diff --git a/analyze_fft2048_iq_F32.cpp b/analyze_fft2048_iq_F32.cpp
index 3262b18..6b50236 100644
--- a/analyze_fft2048_iq_F32.cpp
+++ b/analyze_fft2048_iq_F32.cpp
@@ -38,6 +38,10 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
+
+// *******************   TEENSY 4.x  ONLY   *******************
+#if defined(__IMXRT1062__)
+
 #include <Arduino.h>
 #include "analyze_fft2048_iq_F32.h"
 
@@ -235,3 +239,4 @@ void AudioAnalyzeFFT2048_IQ_F32::update(void)  {
        break;       // From case 15
     }  // End of switch & case 15
   }  // End update()
+#endif
diff --git a/analyze_fft2048_iq_F32.h b/analyze_fft2048_iq_F32.h
index f48f7ec..2aa2577 100644
--- a/analyze_fft2048_iq_F32.h
+++ b/analyze_fft2048_iq_F32.h
@@ -95,6 +95,8 @@
 #define analyze_fft2048iq_h_
 
 // ***************  TEENSY 4.X ONLY   ****************
+// Use 1024 size, or smaller, for Teensy 3.x
+#if defined(__IMXRT1062__)
 
 #include "Arduino.h"
 #include "AudioStream_F32.h"
@@ -298,3 +300,4 @@ private:
     }
   };
 #endif
+#endif