diff --git a/src/decode.c b/src/decode.c
index a29c6a46e..dcd11eb5d 100644
--- a/src/decode.c
+++ b/src/decode.c
@@ -199,7 +199,7 @@ _setimage(ImagingDecoderObject *decoder, PyObject *args) {
             state->bytes = (state->bits * state->xsize + 7) / 8;
         }
         /* malloc check ok, overflow checked above */
-        state->buffer = (UINT8 *)malloc(state->bytes);
+        state->buffer = (UINT8 *)calloc(1, state->bytes);
         if (!state->buffer) {
             return ImagingError_MemoryError();
         }
diff --git a/src/encode.c b/src/encode.c
index f92ba62c2..c47255952 100644
--- a/src/encode.c
+++ b/src/encode.c
@@ -264,7 +264,7 @@ _setimage(ImagingEncoderObject *encoder, PyObject *args) {
         }
         state->bytes = (state->bits * state->xsize + 7) / 8;
         /* malloc check ok, overflow checked above */
-        state->buffer = (UINT8 *)malloc(state->bytes);
+        state->buffer = (UINT8 *)calloc(1, state->bytes);
         if (!state->buffer) {
             return ImagingError_MemoryError();
         }
diff --git a/src/libImaging/Jpeg2KDecode.c b/src/libImaging/Jpeg2KDecode.c
index f086848e9..6af0f2eae 100644
--- a/src/libImaging/Jpeg2KDecode.c
+++ b/src/libImaging/Jpeg2KDecode.c
@@ -861,6 +861,10 @@ j2k_decode_entry(Imaging im, ImagingCodecState state) {
                 state->state = J2K_STATE_FAILED;
                 goto quick_exit;
             }
+            /* Undefined behavior, sometimes decode_tile_data doesn't
+               fill the buffer and we do things with it later, leading
+               to valgrind errors. */
+            memset(new, 0, tile_info.data_size);
             state->buffer = new;
             buffer_size = tile_info.data_size;
         }