diff --git a/include/benchmark/benchmark_track.h b/include/benchmark/benchmark_track.h
index 3f6e91a1a..a61236c8b 100644
--- a/include/benchmark/benchmark_track.h
+++ b/include/benchmark/benchmark_track.h
@@ -60,7 +60,7 @@ benchmark_debug_syscall_start(word_t cptr, word_t msgInfo, word_t syscall)
     seL4_MessageInfo_t info = messageInfoFromWord_raw(msgInfo);
     lookupCapAndSlot_ret_t lu_ret = lookupCapAndSlot(NODE_STATE(ksCurThread), cptr);
     ksKernelEntry.path = Entry_Syscall;
-    ksKernelEntry.syscall_no = syscall;
+    ksKernelEntry.syscall_no = -syscall;
     ksKernelEntry.cap_type = cap_get_capType(lu_ret.cap);
     ksKernelEntry.invocation_tag = seL4_MessageInfo_get_label(info);
 }
diff --git a/libsel4/include/sel4/benchmark_track_types.h b/libsel4/include/sel4/benchmark_track_types.h
index 54c680613..48db19239 100644
--- a/libsel4/include/sel4/benchmark_track_types.h
+++ b/libsel4/include/sel4/benchmark_track_types.h
@@ -43,10 +43,10 @@ typedef struct PACKED kernel_entry {
         };
         /* Tracked kernel entry info filled from outside this file */
         struct {
-            seL4_Word syscall_no: 3;
+            seL4_Word syscall_no: 4;
             seL4_Word cap_type: 5;
             seL4_Word is_fastpath: 1;
-            seL4_Word invocation_tag: 20;
+            seL4_Word invocation_tag: 19;
         };
     };
 } kernel_entry_t;