diff --git a/src/compress_zlib.cpp b/src/compress_zlib.cpp
index 0481ab91..ca5846a7 100644
--- a/src/compress_zlib.cpp
+++ b/src/compress_zlib.cpp
@@ -210,7 +210,8 @@ int upx_zlib_test_overlap  ( const upx_bytep buf, unsigned src_off,
     // Note that Packer::verifyOverlappingDecompression() will
     // verify the final result in any case.
 
-    unsigned overlap_overhead = src_off + src_len - *dst_len;
+    unsigned dlen = *dst_len;
+    unsigned overlap_overhead = src_off + src_len - dlen;
     //printf("upx_zlib_test_overlap: %d\n", overlap_overhead);
 
     upx_bytep const dst = (upx_bytep)malloc(src_off + src_len);