diff --git a/libAACdec/src/aacdecoder.cpp b/libAACdec/src/aacdecoder.cpp
index 24907ee..8993927 100644
--- a/libAACdec/src/aacdecoder.cpp
+++ b/libAACdec/src/aacdecoder.cpp
@@ -775,7 +775,7 @@
     /* For every AU get length and offset in the bitstream */
     prerollAULength[i] = escapedValue(hBs, 16, 16, 0);
     if (prerollAULength[i] > 0) {
-      prerollAUOffset[i] = auStartAnchor - FDKgetValidBits(hBs);
+      prerollAUOffset[i] = auStartAnchor - (INT)FDKgetValidBits(hBs);
       independencyFlag = FDKreadBit(hBs);
       if (i == 0 && !independencyFlag) {
         *numPrerollAU = 0;