diff --git a/libavcodec/wma.h b/libavcodec/wma.h
index 4aad713fa8..ec618d1e64 100644
--- a/libavcodec/wma.h
+++ b/libavcodec/wma.h
@@ -123,6 +123,7 @@ typedef struct WMACodecContext {
     uint8_t last_superframe[MAX_CODED_SUPERFRAME_SIZE + AV_INPUT_BUFFER_PADDING_SIZE]; /* padding added */
     int last_bitoffset;
     int last_superframe_len;
+    int exponents_initialized;
     float noise_table[NOISE_TAB_SIZE];
     int noise_index;
     float noise_mult; /* XXX: suppress that and integrate it in the noise array */
diff --git a/libavcodec/wmadec.c b/libavcodec/wmadec.c
index e814007ead..adf8e491c1 100644
--- a/libavcodec/wmadec.c
+++ b/libavcodec/wmadec.c
@@ -586,6 +586,9 @@ static int wma_decode_block(WMACodecContext *s)
                 s->exponents_bsize[ch] = bsize;
             }
         }
+        s->exponents_initialized = 1;
+    }else if (!s->exponents_initialized) {
+        return AVERROR_INVALIDDATA;
     }
 
     /* parse spectral coefficients : just RLE encoding */