diff --git a/libc/bionic/pthread_debug.cpp b/libc/bionic/pthread_debug.cpp
index 21eac63..f8f0c59 100644
--- a/libc/bionic/pthread_debug.cpp
+++ b/libc/bionic/pthread_debug.cpp
@@ -116,7 +116,7 @@
 static const char* const kEndBanner =
         "===============================================================";
 
-extern char* __progname;
+extern const char* __progname;
 
 #define STACK_TRACE_DEPTH 16