diff --git a/libavcodec/ac3dec.h b/libavcodec/ac3dec.h
index 91462d9f4f..b661308000 100644
--- a/libavcodec/ac3dec.h
+++ b/libavcodec/ac3dec.h
@@ -91,7 +91,7 @@ typedef struct {
 
 ///@defgroup aht adaptive hybrid transform
     int channel_uses_aht[AC3_MAX_CHANNELS];                 ///< channel AHT in use     (chahtinu)
-    int pre_mantissa[6][AC3_MAX_CHANNELS][AC3_MAX_COEFS];   ///< pre-IDCT mantissas
+    int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][6];   ///< pre-IDCT mantissas
 ///@}
 
 ///@defgroup channel channel