diff --git a/libavcodec/iirfilter.c b/libavcodec/iirfilter.c
index 6133a54055..832559cfea 100644
--- a/libavcodec/iirfilter.c
+++ b/libavcodec/iirfilter.c
@@ -269,7 +269,7 @@ void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
 
 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c,
                        struct FFIIRFilterState *s, int size,
-                       const float *src, int sstep, void *dst, int dstep)
+                       const float *src, int sstep, float *dst, int dstep)
 {
     if (c->order == 4) {
         FILTER_BW_O4(float, FLT)
diff --git a/libavcodec/iirfilter.h b/libavcodec/iirfilter.h
index c2484e23d3..b29e035811 100644
--- a/libavcodec/iirfilter.h
+++ b/libavcodec/iirfilter.h
@@ -117,6 +117,6 @@ void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterSta
  */
 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs,
                        struct FFIIRFilterState *state, int size,
-                       const float *src, int sstep, void *dst, int dstep);
+                       const float *src, int sstep, float *dst, int dstep);
 
 #endif /* AVCODEC_IIRFILTER_H */