diff --git a/src/bench/checkblock.cpp b/src/bench/checkblock.cpp
--- a/src/bench/checkblock.cpp
+++ b/src/bench/checkblock.cpp
@@ -22,7 +22,7 @@
                        (const char *)&block_bench::block413567[sizeof(
                            block_bench::block413567)],
                        SER_NETWORK, PROTOCOL_VERSION);
-    char a;
+    char a = '\0';
     stream.write(&a, 1); // Prevent compaction
 
     while (state.KeepRunning()) {
@@ -37,7 +37,7 @@
                        (const char *)&block_bench::block413567[sizeof(
                            block_bench::block413567)],
                        SER_NETWORK, PROTOCOL_VERSION);
-    char a;
+    char a = '\0';
     stream.write(&a, 1); // Prevent compaction
 
     const Config &config = GetConfig();