diff --git a/libbacktrace/BacktraceMap.cpp b/libbacktrace/BacktraceMap.cpp
index b3b4300..78f5b6b 100644
--- a/libbacktrace/BacktraceMap.cpp
+++ b/libbacktrace/BacktraceMap.cpp
@@ -103,7 +103,7 @@
 
 #if defined(__APPLE__)
   // cmd is guaranteed to always be big enough to hold this string.
-  sprintf(cmd, "vmmap -w -resident -submap -allSplitLibs -interleaved %d", pid);
+  sprintf(cmd, "vmmap -w -resident -submap -allSplitLibs -interleaved %d", pid_);
   FILE* fp = popen(cmd, "r");
 #else
   // path is guaranteed to always be big enough to hold this string.