diff --git a/src/streams.h b/src/streams.h
--- a/src/streams.h
+++ b/src/streams.h
@@ -324,17 +324,15 @@
 
         // Read from the beginning of the buffer
         unsigned int nReadPosNext = nReadPos + nSize;
-        if (nReadPosNext >= vch.size()) {
-            if (nReadPosNext > vch.size()) {
-                throw std::ios_base::failure(
-                    "CDataStream::read(): end of data");
-            }
-            memcpy(pch, &vch[nReadPos], nSize);
+        if (nReadPosNext > vch.size()) {
+            throw std::ios_base::failure("CDataStream::read(): end of data");
+        }
+        memcpy(pch, &vch[nReadPos], nSize);
+        if (nReadPosNext == vch.size()) {
             nReadPos = 0;
             vch.clear();
             return;
         }
-        memcpy(pch, &vch[nReadPos], nSize);
         nReadPos = nReadPosNext;
     }